Green’s Dictionary of Slang

(UK Und.) money.

c.1698		B.E. Dict. Canting Crew n.p.: Prey c. Money.
1728		J. Dalton Narrative of Street-Robberies 8: They us’d him only as a Baggage Man; that is, to loop off with the Cole when they had made a Prey.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.