Green’s Dictionary of Slang

duckies n.2

[ducat n. (1)]

(US black/campus) money.

[US]R. Klein Jailhouse Jargon and Street Sl. [unpub. ms.].
[US]Eble Sl. and Sociability 52: Today’s money is duckies; in Captain Grose’s time ‘money’ was balsam.