Green’s Dictionary of Slang

cuckoos n.

[ety. unknown; link to dial. cuckoo-penny, a penny that if turned in the pocket on hearing the first cuckoo, will guarantee cash for the next year]

money.

[UK]Passenger of Benvenuto n.p.: [...] they call the purse a leafe, and a fleece; money, cuckoes, and aste, and crowns [F&H].