blow someone’s head, v.² — Green’s Dictionary of Slang

blow someone’s head v.²

also blow someone’s skull

(US) to fellate.

1970		E. Thompson Garden of Sand (1981) 82: Five bucks a hole. Twenty, blow your skull.
1992		R.C. Cruz Straight Outta Compton 23: I’d be the first to admit that your momma blew my mind [...] but she blew my head first.