I think the derivation pretty well agreed and authenticated in a few cases, Nigel ~~ esp those I named in first couple of posts: jass, rock'n'roll, boogie-woogie, jive...

But even then, I accept that the danger of too unquestioningly embracing the folk-etymology fallacy needs to be recognised, and accept the validity of the point you make and the possibility you suggest.

With many of the others, I agree, the chicken·&·egg question even more obviously rears its head.

~M~