Green’s Dictionary of Slang

(US) a cry of warning.

1927		F.M. Thrasher Gang 58: [in context of street crap-shooting] ‘Jigs, de bulls!’ someone would shout, and they would scatter.
1939		‘The Riggers’ Song’ in C.H. Ward-Jackson Airman’s Song Book (1945) 99: Jigs, Jigs, syrup of figs.
1942		N. Algren Never Come Morning (1988) 72: All they’ll do is holler jigs for me in case the cops show.