I think the term is definitely "African American". It comes from the jazz musician. Wonder if the term has something to do with "getting away with something."(Being paid for doing something that was less than musically demanding.) There was a period in the era of be-bop where a "gig" might be looked at as a necessary evil. A "general business" or "casual" gig would not feature innovative jazz since it would be over the heads of the clients. A wedding gig or a dance gig would be seen as a way to finance the practice time of a dedicated jazz musician who would play at a session. Later, sessions seem to turn into paid gigs. A lot of the late 50's musicians had a disdain for "general business" or "casual" gigs. This changed pretty soon when the "bread" ran out. Even to this day, though, there are jazz players who still think it beneath them to take a "GB" or "Casual". "General Business" is back East whereas "Casual" is California.

Frank Hamilton