As to if and when such meanings evolved or developed ~~ if indeed they did: Nigel's strictures and queries above are by no means to be discounted ~~ it is often difficult to ascertain. Words and phrases will often have a sort of underground connotation among an ingroup [see Peter Wildeblood's 1950s book 'Against The Law' for how that meaning of 'gay', now the primary meaning which has driven out the 'real' meaning, was restricted at the time of the notorious Lord Montagu trial to the homosexual community. Another example ~ my first wife who was a court reporter was amazed in 1959 that I knew the word 'flasher', which was at the time only used by press, police, court officials; but I had learnt it in the army from a fellow National Serviceman who had been a local paper reporter ~~ & so on].

So the point I make is: that it is always possible that a player of the music who is inward with one of these esoteric 'underground' meanings will mischievously, perhaps as a sort of joke on the outside community, use it of the music he has pioneered, so that the word 'escapes' into the broader, 'vanilla' society without its original connotation being suspected.

~M~