Green’s Dictionary of Slang

1. (US) a general intensifier, positive or negative according to context.

1944		R. Brooks Brick Foxhole 12: That’s the best humpin’ thing about this base [HDAS].
1972		B. Hannah Geronimo Rex 241: Six inches of black humping air! Have you smelled what’s coming out of there?

2. (US black) very attractive.

1994

G. Smitherman Black Talk.