Just to toss something out among those who know much more than me...
In my professional world there is a ton of vocabulary for sword polishing, parts of swords, polishing techniques, types of swords, and on and on and on. I could probably name a handful of Japanese words that are *for the most part* interchangeable that refer to the edge of a Japanese sword. However, that said, there are usually some subtle differences here and there where when used in context the word might have additional meanings or a different "feel" to it. Just to pull two out at random, the "ha" of a sword and the "yakiba" of a sword. The ha is generally used to refer to the edge. Period. Yakiba is also used to refer to the edge. Except when someone is also making a point about how the edge of Japanese swords are steel in a hard and relatively brittle state (as contrasted with the softer body or the lower carbon soft core or ...). So yakiba can have some additional meaning if the person intends. But many times it doesn't. And sometimes it's just your best guess if the person who wrote something meant to include the additional connotation and "flavor" of the word.
The reason I bring this up is that the craft and art of the Japanese sword has a history that spans over 1000 years. There are so many terms that evolved along the way, some with subtle differences in meaning. And I would hazard to say that most of those words have meaning that has evolved and morphed over time with usage, the style of the day, the tone of the day, etc. What they mean today is a snapshot in time of things that likely varied tremendously, sometimes in major ways, but most of the time just in subtle, difficult to express ways. Many meanings likely lost. Many new meanings gained. It's part of the evolution of something that is complex, that is hard sometimes to describe, that needs slightly different words now and then to encapsulate something new (the glittery mist called "utsuri" that formed in the ji of old Bizen school pieces was something "new" so a word is created. The Yamato-den style of sword making creating what we call a "high shinogi" by deciding to adjust the balance of their swords to make them more robust (slightly thicker at the ridge) but then pulling the shinogi-ji surface back to angle back at the mune ("back of the sword) giving them "correct" balance but allowing for tougher, blades), and on and on. Some words retain a rather specific meaning but many more arrive to cover subtle nuance and without question many times will lose some distinctions, gain new ones, etc. Heck, just read through many of the posts here showing each person's understanding of just what aikido *is* to see how redefinition occurs in real time.
So I suppose I'm just saying something really obvious. And when I started Aikido and got serious about learning more about the history, techniques, names, etc. and started buying up books left and right from other styles not to mention going "outside the box" to play with folk doing stuff other than aikido that was related to aikido, well, I was struck that what we have here is a similar bunch of words that reveal a rich history that evolved within a very short time. Numerous prominent teachers working with things that were loosely defined. And many of those teachers splitting off at different times sometimes working hard to systematize *their* version of the art.
It would be great if one could find a history to show how the terminology can be tied off, arranged, and neatly presented with a fancy bow on top. But it strikes me the odds of that are vanishingly small. This is not to say the discussion is for naught -- it is a great discussion and I've learned a few things. But it strikes me as not that much different than the terminology of the Japanese sword that sometimes has words where differences appear to be random, capricious, and/or sometimes completely baffling.
The drawback here, of course, is that it makes for all sorts of "flights of fancy" for those who are willing to read things in to everything they hear. And sometimes things like that "stick" with some groups making for really frustrating conversations and opinionated, passionate folk getting banned from discussion forums...
And fwiw, one late night in the bar after a sword show I was talking with a rather prominent smith from Japan who was visiting. I was asking questions about a few things and he was interested in some of the "off the beaten track" some western smiths doing Japanese style swords were up to. We were trying to talk about a detail of heat treating and due to language issues it wasn't going all that great. But he laughed and told me that it wasn't really the English/Japanese that was the problem. He said that even in Japan smiths will have to go in to the workshop, fire up the forge, and start hammering steel to convey anything that's really interesting. Even with a robust terminology the words can get in the way of understanding.
So cool thread and interesting discussion. But in the end... Shrug...
Just an observation reading the thread.