closed as off topic by TimLymington, Matt E. Эллен♦, F'x, simchona, kiamlaluno Sep 7 '11 at 11:15
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The letter c was already taken for change so they couldn't use "copy". They needed another word. They couldn't use w for write, because it already means word. They couldn't use p for put, because it was already used for paste. And so on. (http://www.gammon.com.au/smaug/vi.htm has a list of vi commands.) Eventually someone came up with a word, yank, that didn't start with a letter that was already being used, and that at least vaguely carried the right meaning. Plus for some people, they remember it as the last letter of copy. The fact that you can think of words that better mean "copylike behaviour" isn't really the point.
Yank in the sense of pull is a BE term from early least 1800s - which makes sense in terms of "grab a copy of". It's still a common term for pull sharply.
So if not older than yank (as a term for American) it is older than emacs (or even vi)