Green’s Dictionary of Slang

(UK Und.) a pickpocket; also as foyl someone’s cloy v.

1660		Wandring Whore III 78: By that means [she] foyl’d his cloy of above ten pounds.
1661		Wandring Whore V 16: Foylers, Kid-nappers, Decoys, Hectors, Pimps and Trapanners.
1671		‘L.B.’ New Academy of Complements 204: The sixth is a Foyl-cloy that not one Hick spares.
c.1698		B.E. Dict. Canting Crew n.p.: Foyl-cloy, c. a Pickpocket, a Thief, a Rogue.