Green’s Dictionary of Slang

(US black) competing in rounds of ritualized mockery.

1942		Pittsburgh Courier (PA) 22 Aug. 7/6: Sigging — (Scoring, doing all right).
1971		H.E. Roberts Third Ear n.p.: signifying, siggin(g) v. language behavior that makes direct or indirect implications of baiting or boasting, the essence of which is making fun of another’s appearance, relatives, or situation. Variations include joning, playing the dozens, screaming on, sounding.