Episode 40 of the Tai Chi Notebook Podcast is out on Spotify, Apple Podcasts and elsewhere.
I’m joined by my friend Benjamin Palmer. Ben has been running a Xing Yi Quan training group in deepest darkest Somerset for a good few years now, but Ben has also been training Mishima Kempo, an eclectic Japanese martial art and is thinking of starting a class in that soon.
We share the same Xing Yi teacher, Damon Smith who has been a previous guest on my show.
I visited Ben’s Xing Yi class a couple of weeks ago to teach his group some grappling and afterwards we sat down for a chat, and a nice cup of tea, so here we are in Ben’s kitchen!
How to time you strikes with your footwork, a video lesson
Sun Lu Tang, performing xing yi’s Zuan Quan.
Xing yi is a martial art I’ve got a lot of time for. The first thing I noticed about it was its approach to stepping and how different it was to other Chinese martial arts like tai chi, for example. In fact, the only other martial art I can think of that uses a similar type of stepping is yi quan, which is a derivative of xing yi, and perhaps Sun Style Tai Chi, which is obviously influenced by xing yi because it was the main martial art of the founder, Sun Lu Tang.*
When approaching xing yi for the first time, most people seem to be more interested in what’s going on in the body because it is an internal art. I think that, in a way, the label ‘internal’ is something of a blessing and a curse for xing yi because it leads to a lot of intellectualising about it, which is sometimes unnecessary. Before you need to start worrying about things like the internal workings of the body, I think you should be focusing on the footwork of xing yi, because that’s the key to getting the right feel for the art.
Xing yi stepping is different
It’s not like all Chinese martial arts don’t use stepping, (of course they do), but there’s something really nice and practical about the way xing yi uses stepping and striking in harmony*. If you look at a random xing yi link (its name for forms) then no step is wasted – something is happening on every step.
But it goes a bit deeper than than – the timing of what is happening is the thing to look for. The strikes combine with the stepping to put your mass into each strike, so rather than hitting people with just the weight of an arm, you’re hitting them with your whole body weight behind the arm.
I made a video about the timing of xing yi steps and strikes before and I’ve talked about xing yi stepping basics before, but a viewer of one of my YouTube channels, contacted me recently asking to know more about it, so I thought I’d make another video.
So, here it is – I’m demonstrating some standard ‘jab, cross, hook’ strikes on some pads first. There’s nothing special about this, then I look at how it would change if you were going to adopt the xing yi footwork. I show this with the weight staying on the back leg first, then I show how you’d do it with a palm strike and the weight on the front leg – in the way you do it with Bear (Xiong Xing). And then I show some xing yi movements in a linking form, where the steps and the striking are using the same timing. This is a mix of elements and animals.
Is there anything ‘internal’ in this? No, it’s just the mechanics of stepping and striking done together in the general way xing yi uses them. However, my controversial opinion (sorry, I’m trying not to get into arguments these days) is that you need to get this down first before you start with the more subtle internal stuff.**
* Yes, I’m sure there are other Chinese martial arts that use this sort of stepping sometimes – talking in generalities helps make a point, but it is rarely accurate.
** Xing yi is a big art, what I’m talking about is a feature of Hebei Xing Yi – other styles may vary and not use the same sort of footwork. I’m not attacking the way you do XY or the way your Sifu taught you.
Traditional martial arts, which are perhaps better described as “martial arts that are not sports”, tend to have a lot of forms, or kata. I’m thinking of karate, tai chi, wing chun, choy li fut, etc.
But what exactly is the role of kata, or forms? And has it changed over time?
In this new episode of the Heretics podcast I discuss the role of kata with Damon Smith who has extensive experience in various martial arts over decades.
It certainly became very trendy once MMA became a big deal to describe forms as useless, however, I think they do have uses, even today. As usual Damon has some pretty interesting insights into how forms have changed over time, and he can look back to the way they used to be trained in the 1980s compared to today.
In this podcast I talk to internal martial artist Ethan Murchie about this teacher Vince Black from whom he learned xing yi mixed with elements of Sufism and Shamanism, as well as the North American Tang Shou Tao Association which Vince set up and which is still running today.
We also discuss how traditional arts can survive alongside MMA, the Yellow Emperor’s Classic of Internal medicine (the Huangdi Neijing) which Ethan teaches through his Living Neijing website, the meaning of Chinese terms like qi, peng, lu, ji and an, as well as his tai chi teacher Liang Dehua and the Yang Shouhou lineage of Yang family tai chi.
And why you shouldn’t train with weights when developing your qi
Mike Sigman has sent me an article to publish on this blog. I don’t normally publish other people’s work, or agree to their requests, but I’ll make an exception because it will hopefully generate some discussion. Regardless of how you feel about him, there’s is always a real depth to Mike’s writings and ideas that you can get a lot from, that you don’t really find anywhere else.
The article is primarily about one of the trickiest subjects in Chinese martial arts – qi (or chi).
I have a few thoughts about it:
1) The article starts by trying to “separate the skin-related qi, which includes the subconscious mind’s involvement, from the theoretical qi of traditional Chinese medicine”.
To some, particularly those people who relish Chinese history and the evolution of the concept of qi as it appears in Taoist thought, or medicine, that just won’t be acceptable, but I think this works for me. It moves the discussion into the realm of the physical and practical. It becomes a feeling and a doing thing.
2) It appears to be written partly as a reaction to a recent trend of mixing, or doing, Chinese martial arts conditioning through the medium of kettle bell or weights training. The question is, is that a waste of time if you want to get to the root of the subject, which is what the Chinese martial artists call qi?
Look, I don’t think there’s anything wrong with making yourself physically stronger at all. In fact, it’s obviously advantageous if you’re learning martial arts… But the article states that to master the internal movement, “the body must be completely retrained to learn to move with the qi, jin, and dantian”, and using weights will not help you in that respect. If you have retrained the body, then you could probably add them.
3) As I’ve said, nobody else really talks about this stuff, or if they do it’s watered down with a lot of other guff. If the article is correct on qi then what exactly are all the big names in modern tai chi seminar circuit and online courses out there actually teaching? Because they talk about qi a lot… but they don’t approach it in the same way as this article does, at least as far as I can see.
4) The article describes internal movement, quite simply and quite succinctly: “Ultimately, you develop a form of movement that uses the solidity of the ground as the focus of all forces to and from the body, while the qi covering of the body is manipulated by the lower-body and the middle to bring power to the arms and upper body.”
I find it hard to disagree with that definition, probably because it’s pretty broad. Sure, we can argue over what the “middle” is, or what the “lower-body” means,etc.. but as a succinct definition, it’s not half bad.
Now, let’s move on to how you do it…
The article talks about breathing exercises as a starting point: “Breathing techniques that stretch the surface of the skin and the involuntary muscle layers are the usual start of the progression.”
Now, I have personally trained in some of the methods that Mr Sigman uses (there’s a link to a video at the end of the article), and experienced what he’s talking about, and I’d agree that I can feel what he’s talking about. But I wouldn’t count myself as an expert in it, or knowledgeable about anything to do with it beyond the initial foot in the door stages, however, I have found that alone to be incredibly valuable and shone a light on some of the other things I was already doing. Even getting a foot in the door took a lot of work and a lot of time.
Anyway, I’ll leave you to read the article now and feel free to comment with your thoughts below.
Graham
Practical Development of Qi
And why you shouldn’t train with weights when developing your qi
by Mike Sigman, March 2025
Discussing qi is difficult because the definition of qi has become a bird’s nest of related topics. Let’s try to narrow the discussion and then describe an approach to practical development.
Most of the skills related to qi, in the physical body, have to do with an area near the skin of the body that is referred to as the “protective qi” or “wei qi”. While the protective qi is often referred to as an “energy”, it is actually a physical set of tissues that is controlled via the autonomic nervous system … but when you learn to control it via the subconscious mind, it does indeed feel sort of like an “energy” because it is apart from the topical sensations of the somatic nervous system, and the qi indeed feels odd, like an energy.
So, let’s separate the skin-related qi, which includes the subconscious mind’s involvement, from the theoretical qi of traditional Chinese medicine: that’s where most of the confusion lies. The skin-related qi and the subconscious mind are the artifacts which give us heightened toughness of the skin, odd sensations of qi, added strength by supplemental our muscle-bone strength, and dantian control of the body as whole connected by skin-related qi, among other things. Jin forces, the manipulation of the solidity of the ground and/or downward forces of gravity, are also the product of the skin-related qi: jin is defined as “the physical manifestation of qi” in many Chinese sources.
The qi of traditional medicine theory is/was an effort to explain the workings of strength, including the strength of our involuntary systems. We don’t need to know all the theories about meridians, putative different types of qi, etc., in order to develop the qi. Breathing exercises and focused physical and mental exercises are more important than complex qi-paradigm explanations.
The skin-area wei qi is initially controlled by respiration and “breathing exercises” are our initial approach to control and development of the qi tissues. During inspiration, if we are slightly extended or stretched out, we can feel a slight inward pulling of the tissues of the fingers and hand. Other areas of the body, upon being slightly stretched taut, can also be felt during the inhale, but many tissues in other areas of the body can’t be felt. They must be developed over time by breathing exercises before we can feel them respond to our breathing and before we can develop them further.
Some Chinese texts mention the fact that this superficial qi is something that animals still use (think of a horse quivering its flanks, for example), but which has atrophied in humans over the course of evolution. In order to regain our qi, we must use deliberate exercises of breathing, mental imagery, and posture manipulation.
Training the Qi in General Movement
Jin force-manipulation is a product of the qi tissues applying stressors within the body’s frame. That’s why jin is defined as “the physical manifestation of the qi”, among other things. We use jin unconsciously in our everyday movements, so another common definition of jin is as an “intrinsic strength”. The full-blown traditional movement methodology that permeates the Chinese (and related) martial arts involves both qi and qi’s subset, jin. Qi and jin. Jin forces are the mind-directed forces from the ground and gravity; qi can be thought of, in a simplified sense, as a superficial muscular layer that connects the whole body.
The basic idea of movement with qi and jin is that the power from the ground and lower body is used as the power source for the upper body. The qi and the jin work from the lower body (including the middle/dantian), so what we have with “internal” movement is a system where the arms and hands are controlled and powered by the lower body and the middle.
The general admonition is that muscle and power are used in the lower body, as needed, while the upper body is moved without the use of local muscle. I.e., a person has to learn to control his/her upper body via manipulation of the lower body and the middle. The person who thinks the internal arts would be best supplemented with typical weight workouts at the gym has lost the plot and is giving away a total lack of understanding about how the “internal” martial arts work.
Developing the Qi
Jin skills are actually fairly easy to learn, although it generally takes a few knowledgeable pointers and some personal, hands-on demonstrations to get someone started. There are a number of written attempts at jin explanations on the internet, particularly through the 6H forum.
Qi is difficult to develop because it takes time and the feelings we need to focus our attention are tenuous at first. Breathing techniques that stretch the surface of the skin and the involuntary muscle layers are the usual start of the progression. Many traditional Chinese martial arts talk about “100 Days” of breathing exercises to develop the qi to a usable status.
Movement of the involves directing all forces upward from the solidity of the ground (so you must “sink your qi”) or use the weight of the body as a basis for downward movement.
Ultimately, you develop a form of movement that uses the solidity of the ground as the focus of all forces to and from the body, while the qi covering of the body is manipulated by the lower-body and the middle to bring power to the arms and upper body.
All Asian martial arts that are labelled as “internal” martial arts, formal calligraphy, qigongs, traditional dance, etc., use this combination of qi and jin for movements. Learning the external choreography and appearance of a martial art, a qigong, etc., no matter how much it resembles the movements of an expert, will not be correct until the system of movement is changed over to the qi, jin, and dantian type of movement.
Almost all of the movements we so often see in western semblances of “Tai Chi”, Aikido, Xingyiquan, Baguazhang, etc., are based from normal movement parameters, rather than qi and jin mechanics and it will take effort to re-learn these arts with the correct movement basis. There is an old saying to that effect: “Taijiquan is easy to learn, but difficult to correct”. So, if your goal is to learn Taijiquan, Aikido, or related arts, remember that all the talk about “relaxation”, “don’t use weights”, etc., is because the body must be completely retrained to learn to move with the qi, jin, and dantian.
Here’s a video of Chen Zhaosen, with translation by John Prince, teaching basic movement drills for the Chen-style Taijiquan. Notice his comment about no strength in the upper body, but whatever strength you need in the lower body. https://vimeo.com/141009942
Hello! Happy Year of the Snake, dear reader. On an occasion such as this is would normally be customary for a tai chi blog like mine to do a little post about the influence of the snake on tai chi, kung fu and Chinese culture in general.
Snake is, after all, one of the five main Shaolin kung fu animals, one of the 12 main xing yi animals and frequently appears as a menu item in Chinese restaurants, er no, sorry, I mean, appeared in Kung Fu Panda!
But, no! I’m not going to do that; partly because it’s such an obvious thing to do that I’ve done it before, and I hate being predictable, or at least repeating being predictable, but also because I’ve just recorded an excellent conversation for my next podcast with Australian national treasure and sometimes-Chinese-martial-arts-practitioner, Simon Thakur of Ancestral movement about finding your inner, ancestral animal, including, of course, the snake, and I just need to find the time to get on with editing it so I can get it out to you lovely people.
I think that what Simon says about our human connection to snake-style movement is probably more valuable than whatever I’ve got to say on the subject of our slithering cousin. So, I’ll leave the snake talk until the podcast comes out!
Simon Thakur, trying to locate his inner snake while doing an impromptu bit of Fox Trot in The Bush.
In the meantime, while you wait for that podcast to properly percolate (all the best things take time) I’ll leave you with a thought. “Tai Chi is more than the techniques, it’s the jins that make it interesting”.
If you listened to my last podcast with the esteemed Alan Wycherley of ‘In Defence of the Traditional Arts’, you might be forgiven for thinking that I’m all about training tai chi techniques. Now, while I’ve no objection to practicing a Repulse Monkey or a Part Wild Horse’s Mane (or two), or even a Snake Creeps Down, I definitely agree with the statement that tai chi is more than the moves. In fact, I think we can probably agree that tai chi applications aren’t that great as martial techniques. There are (shock!) other martial arts that have more effective techniques. Hello, Brazilian Jiu-Jitsu, I’m looking at you. Hello, Choy Li Fut. Hello, Western Boxing. Hello, Muay Thai, stop hiding at the back! Yes, all these martial arts have techniques that I would probably put ahead of anything found in a tai chi form, regardless of style. They’re practical and effective. And yet, I practice tai chi. So, why is that?
What tai chi has, and emphasises over techniques, are the eight energies – the jins: Peng, lu, ji, an, etc.. What you are doing when you practice a tai chi form is emphasising energy changes using these eight over technique. Flowing from one to the other a bit like a river flowing along smoothly. Sometimes there are fast bits, sometimes there are slow bits, sometime the river turns one way or another, but its energy flow keeps going.
When I practice other martial arts, my emphasis is more on technique. When I practice tai chi I can relax and get more inside the movement and concentrate on the energy flow.
And of course, in tai chi push hands you get to interact your energy flow with the energy flow of another person in a live situation, and that’s extremely valuable for developing martial ability. Techniques are another thing.
Now, if the analogy of a river doesn’t work for you then think of something else… perhaps, a snake? Snakes can flow along smoothly, they can change direction sharply and they can be incredibly powerful or incredibly quick, as well as slow and suffocating. They’re a great example of energy changes.
Homework
In preparation for my next podcast allow me to recommend a documentary by professional paleontologist and evolutionary biologist Neil Shubin called Your Inner Fish. (He’s written a book of the same name, if you prefer to read about him). Snakes come out to play in episode two. Here you go:
At the recent 2024 Martial Arts Studies conference in Wales I had the good fortune to meet Randy Brown of Mantis Boxing and Brazilian JiuJitsu in Massachusetts, USA. We had a blast at the conference discussing martial history, theory and even demonstrating a few techniques on each other into the small hours in a pub in Cardiff city center! Not only is Randy highly skilled in mantis boxing, but he’s also a black belt in Brazilian Jiujitsu, so we had a lot in common.
When I was exchanging techniques with Randy he noticed that the Choy Li Fut I was showing was identical to moves from a form he knew called gong li quan, which translates as “power-building boxing”. It was a form he had learned that was used as foundational training for various Ching dynasty martial arts, like long fist, eagle claw boxing and praying mantis boxing.
Gōng Lì Quán, or Power Building Boxing, is a unique boxing set from northern China, and is included as a training routine amongst a variety of boxing styles in the north to include: long fist, eagle claw boxing, and praying mantis boxing. This form likely intermixed with the latter two styles when it was included as part of the Jīngwǔ Athletic Association’s fundamental wu shu curriculum. At Jīngwǔ, gōng lì quán was one of the mandatory six empty hand and four weapons sets taught to kung fu practitioners. These ten sets were required as a prerequisite to the study of: xingyiquan, bagua, taijiquan, eagle claw, or mantis boxing; considered by Jīngwǔ founders to be more ‘advanced’ styles.
Our meeting seems to have sparked a desire in Randy to delve further into gong li quan and resurrect this old form he’d forgotten about and try to bring the movement to life with grappling applications. He’s been kind enough to share video of his research.
3 Rings Trap the Moon
This was the original move we discussed in Cardiff, 3 Rings Trap the Moon, which in Choy Li Fut would be a gwa choy (back fist) followed by a sau choy (sweeping fist) followed by a biu choy (an outward forearm strike). Randy shows the original move from gong li quan, then his grappling applications. It’s pretty cool!
Twining Silk Legs
Randy has been updating his blog post with new applications as he goes, so keep checking back. One of his latest is the move Twining Silk Legs:
Twining Silk Legs is two upper cuts followed by two kicks. Again, Randy shows the move and then his grappling interpretation of the applications. What’s really interesting to me is that, once again, there’s a parallel in Choy Li Fut with this move. If you look at the move starting at 1.22 in the following Choy Li Fut video you’ll see what is essentially the same move as Twining Silk Legs – two upwards strikes followed by a kick. (Ok, just the one kick here, not two, but still…)
You could look at this as further proof that gong li quan and Choy Li Fut share a common ancestor back in the mists of time, but since I’d be willing to bet that other Chinese martial arts practitioners would also recognise these moves from their own systems, I’d venture to say that is is further evidence for Randy’s theory that the explosion of different martial styles during the end of the Ching dynasty (which is where we get Choy Li Fut, mantis, Wing Chun and the other well-known styles) was more about branding the martial arts, for commercial reasons, and that they actually shared a common pool of knowledge.
“A question needs to be asked, did ‘Chinese boxing’ of the era, have a similar common pool of knowledge? Qī Jì guāng’s manual would hint at such. Within ‘Chinese Boxing’, attributes, feats, or skills defining one fighter over another became definitive styles of their own right due to events of the time”.
(The Qi Ji Guang he’s referring to is the Ming dynasty general who fought off Japanese pirates and because a hero to the people. He wrote a famous manual which documented the martial arts of the time. The techniques in the manual seem to crop up in all sorts of Ching dynasty martial arts.)
You can learn more about the the tumultuous events of the Ching dynasty and the explosion of martial arts styles that happened during it in Randy’s video of his presentation from the 2019 Martial Arts Studies Conference:
2025 Martial Arts Studies Conference
Today I heard the exciting news that next year’s 2025 Martial Arts Studies Conference will also be held in Cardiff, Wales. This will be the 10th anniversary of the original 2015 conference, which was held on the 10th-12th June in Cardiff, and will be held on exactly the same dates. It’s almost too perfect. See you there?
The Martial Arts Studies Network has also released a new (and free as always) issue 15 – check it out, it’s full of top-quality articles on martial arts. Oh, and don’t forget, I also recorded a podcast with Randy while we were at the conference – here it is:
“The origin of internal arts” is probably what I’d have called this really interesting podcast with Peter Lorge about the history of internal martial arts, however Kung Fu Genius decided to name it “Chinese Martial Arts History is Mostly FAKE” because, well, it probably generates more clicks, or something. Anyway, Lorge turns over a few sacred cows here, and I also liked what he had to say about BJJ.
Have a listen:
I think Peter makes a great point about all these different ‘internal’ things throughout Chinese history all definitely existing, but all being completely separate and unconnected until the 1920s Guoshu Institute needed to create the category of “internal” to exist in opposition to shaolin and external, so it brought them all together. (The gentleman whose name he forgets when talking about this is obviously Sun Lu Tang.)
I do wonder if instead of looking back for mentions of “internal” throughout Chinese history a look back for the phrase Liu He “six harmonies” would make a better connection between the dots of Chinese martial arts history. While the term “Neijia” may not appear very often pre-1920s, Liu He definitely did. If we’re looking at how we got where we are today, then that’s probably a better bet.
This post is going to start somewhere you don’t expect – over 1,000 years ago in Song Dynasty China during which we find the legendary founder of Xing Yi, Yue Fei, a general in the Song Dynasty army, mulling over the advancing (heavily armoured) Jin cavalry, and wondering how his foot soldiers are going to fair against the crushing advance of an army that had destroyed the Liao Dynasty troops, scattering them to the Western regions.
The Jin/Song wars would last a century, starting in 1125, when the Jin attacked the Song after a series of negotiations between the previous allies failed. During this period North and Southern China was effectively separated between Jin and Song, with the Song retreating into the south of China. The Jin advance into southern China in 1130 was stymied by Song generals like Yue Fei and Han Shzhong. Eventually the Song allied with the Mongols in 1233 to defeat the Jin, but the Mongols then went on to defeat their previous allies, the Song, and thus the Yuan Dynasty was born.
But why this history lesson? Well, one weapon that was popular during the Song/Jin wars was the ‘sword breaker’ called a bian, which translates as ‘whip’. But it was a very solid short stick made of iron, not a flexible whip. It was often used on horseback because it was effective against heavily armoured warriors, and the Jin cavalry was very heavily armoured.
The Tai Chi move “Single Whip” (Dan Bian), has the same character for whip as the one used for the ‘sword breaker’. It’s also similar to the characters for ‘shoulder pole’, which I’d previously speculated was a possible origin for the name. But people who are better at Chinese than me have cast doubt on this theory. It seems much more likely that it’s the ‘sword breaker’ weapon that is being referred to, not a shoulder pole.
“Recently I’ve been made aware of some theories about the meaning behind “Single Whip” 單鞭 (dān biān)
Basically the claim is that the posture resembles a farmer carrying something on a pole or yoke and that the name refers to this yoke.
This yoke or shoulder pole is called 扁擔 (biǎndan)
So right away, simply linguistically, this claim is a little bit problematic.
English Character Pinyin Romanization. Single Whip 單 鞭 dān biān Shoulder Pole 扁 擔 biǎndan
We’re dealing with four completely different characters with completely different meanings. The dan in biandan is POLE not single.
To a native Chinese speaker this is like comparing apples to tennis balls. It’s just a ridiculous claim.”
The post goes on to look at the historical record, which is fairly interesting, and makes the case for the bian being the ‘sword breaker’.
Fair enough, the shoulder pole idea was just a theory of mine based on the similar name, and the way it looks. As with all good theories, it can be disproved with evidence. But as I also said in that original post of mine:
“The ‘whip’ could also be used as a weapon in Chinese Marital Arts. Again, it was usually referring to a short stick, not a flexible whip. In the excellent “Chinese Martial Arts Training Manuals” by Brian Kennedy and Elizabeth Guo you’ll find a description of a book called “Tiger Tail Whip” by Jiang Rong Qiao published in 1930. It features a “long routine for the metal tiger tail ‘whip’, which is rigid and actually amounts to a type of cane.””
“Chinese Martial Arts Training Manuals”, by Brian Kennedy and Elizabeth Guo
The ‘sword breaker’ or ‘bar mace’ was certainly more substantial than a cane. As the name implies, it could break swords, but it was also good for attacking heavily armoured soldiers as it could impact the person under the armour. Check out what it could do in this excellent video:
What’s in a name?
But it’s still hard to work out why the Single Whip posture would be named after the ‘sword breaker’ in the first place. I mean, the posture doesn’t resemble the weapon at all… But then I saw something very interesting recently:
“This brick carving is from a tomb of Jurchen Jin (1125–1234), describing a battle between Song and Jin cavalries. The one who faced to us with a sword breaker 锏 might be Jin cavalry, who snatched the pole weapon (三尖两刃刀, lit. ‘Three points double edged blade’ fig. 3) away from Song cavalry and swung his sword breaker 锏 to attack his head from right to left. Song cavalry’s head and helmet were totally whacked. Well, pole weapon user should always keep distance with enemy and, such blunt weapons like mace, sword breaker etc. are really excellent weapon against heavy armor. Picture 2 was drawn by 咪咪妈的刘sir.”
Now, what I notice about this carving, and the painting, is that it isn’t a million miles away from the application of single whip that we practice in our Tai Chi. Check it out:
Maybe that’s where the name “Single Whip” comes from? The application of the move is certainly similar to the way you’d use a ‘sword breaker’ way back in the Jin/Song wars to grab the opponent’s long pole weapon and bash them on the head with your ‘whip’.
But why “single”? Well, it turns out that the ‘sword breaker’ was often a two handed weapon. You had one in each hand, as this carving of the Jin cavalry shows:
You can also see double maces being used by cavalry in the painting that opens this article.
It’s as good an explanation for “single whip” as I’ve read anywhere else. And at least this reasoning makes some sense. At the end of the day, it’s just another theory, ready for some eager beaver to disprove.
The Tai Chi Notebook 