Green’s Dictionary of Slang

(US black) to talk excessively, loudly or inconsequentially.

1962		in B. Jackson In the Life (1972) 163: And I’m sitting up here jawjacking with this other tramp.
1971		T. Whitmore Memphis-Nam-Sweden 87: We was always jaw-jacking about whose outfit was better. [Ibid.] 113: The white dude in front of me was jawjacking with the guy in back of me.
1984		A. Sample (con. mid-1930s-early 1940s) Racehoss 98: [A]nother player spoke up, ‘Say Big Emma, ya’ll cut out all the shit. I ain’ won a bet since ya’ll been jaw-jekin’ [ibid.] (con. 1940s-early 1950s) 128: I followed her back through the house and stopped at the crap table to rejoin the ‘jaw jekin’ session. I listened to my fill of bull.
1992		D. Burke Street Talk 2 34: Ev’ry time I tried jaw jackin’ with Miss Thang, she got so frosted that I fin’lly jus’ folded.