Green’s Dictionary of Slang

(US black) a ritualistic handshake, differing from area to area, involving much slapping of palms, snapping of fingers etc; thus v.

1972		D. Claerbaut Black Jargon in White America 62: dap n. a rather sophisticated or complicated hand greeting used by many black people.
1974		H.L. Foster Playin’ the Dozens 211: I knew I had done something right when one of the students put his hand out for some dap and returned it after I had given him some skin.
1982		(con. 1970) J.M. Del Vecchio 13th Valley (1983) 53: ‘Couple of brothers slappin themselves silly . . .’ ‘That’s the dap. It’s kind of a way to say hi.’ [Ibid.] 391: Egan held his right fist out and Jackson met it with his own right fist as they dapped. The two fists tapped knuckles-to-knuckles and back-to-back. Open hands passed over each other in sensual caresses of brotherhood.
1994		(con. early 1970s) N. McCall Makes Me Wanna Holler (1995) 104: They performed ‘dap’, a handshake greeting in which they went through a long series of syncopated movements, slapping each other’s palms, wrists and elbows in a colorful show of black solidarity.
2002		‘Touré’ Portable Promised Land (ms.) 156: We Words (My Favorite Things) [...] Fox. Dime. Duke. Dap.
2004		T.I. ‘I Can’t Quit’ 🎵 Still in the trap signing your shirts, giving you dap.
2006		J. Ridley What Fire Cannot Burn 59: Eddi and Alcala laughed, dapped.
2008		G. Pelecanos Way Home (2009) 257: Lawrence [...] held out his fist [...] ‘You too good to dap me up?’.
2011		G. Hayward Corruption Officer [ebk] cap. 2: He gave me dap and while I was waiting for C we reminisced.
2021		T. Pluck Boy from County Hell 306: He held up a fist and Jay gave him dap.