Green’s Dictionary of Slang

(US black) a fool, a sucker.

1939		Cab Calloway ‘Jumping Jive’ 🎵 Don’t be an ickaroo / Come on do like the ’gators do. / Hep, hep!
1945		C. Himes ‘The Song Says “Keep on Smiling”’ in Coll. Stories (1990) 90: I’m making plenty right here in this beatup joint jiving these icks.