Green’s Dictionary of Slang

1. to show off; to upstage.

1980

E. Folb Runnin’ Down Some Lines 109: To high sign, to fonk [...] which mean to show off or upstage others.

2. to praise.

1994

C. Major Juba to Jive 178: Fonk [...] v. (1980s–1990s) [...] praise.