Green’s Dictionary of Slang

to cheat, to defraud.

1608		Dekker Lanthorne and Candle-Light Ch. 3: They are glad [...] to fall to Ferret-hunting.
1664		R. Howard The Committee IV i: Ferret him, or he’l never bolt.
1672		J. Lacy Old Troop I i: Thou art call’d Ferret-farm, because thou art so terrible valiant amongst the Country-Bumpkins.
c.1698		B.E. Dict. Canting Crew n.p.: Ferreted c. Cheated.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 76: Ferret — to haunt one for money.