fish-head, n.² — Green’s Dictionary of Slang

fish-head n.²

[among the poor a fish-head was considered a treat or delicacy]

(W.I.) a bribe, a tip.

1956

cited in Cassidy & LePage Dict. Jam. Eng. (1980).

eat fishheads (and scramble for the gills) (v.) (also eat fish)

(US black) to suffer poverty.

1943		D. Burley N.Y. Amsterdam Star-News 13 Mar. 13: It’s frail, eating fishheads and scrambling for the gills.
1944		D. Burley N.Y. Amsterdam News 15 Jan. 10A: The scoffings were slim [...] the cats ate fish in fact ’twas their main dish.