Green’s Dictionary of Slang

(US black) a positive or negative intensifier depending on context; thus exceptionally good or bad, smelling sweet or vile etc.

1968		‘Sl. of Watts’ in Current Sl. III:2 24: Fonky, adj. Nice.
1972		E. Folb Urban Black Argot 138: Fonky, Funky i. something unusual, either good or bad ii. smelly.
1980		E. Folb Runnin’ Down Some Lines 154: Also, the word fonky, which in other contexts means giving off an offensive body odor, takes on a positive meaning in the sexual context. Here it often identifies the good smells connected with good sex.
1992		Eble Campus Sl. Apr. 4: fonk – weird, out-of-touch, ugly. ‘That girl’s hair looks fonk.’.
1994		Rebennack & Rummel Under A Hoodoo Moon 1: I’m out on the bricks of the fonky streets of Fort Worth. [Ibid.] 179: This was when I knew some fonky shit was going down.
2003		G. Leif Bellman Swerve 175: I’d bust some capture doctrine on yo’ fonky selves (make all’yall pay).