Green’s Dictionary of Slang

gull n.

[SE gull, to dupe, to deceive; note gull, simpleton, dupe, despite inclusion in Grose (1785) is SE]

a trickster, a cheat.

[UK]Jonson Every Man In his Humour IV ix: Why how now, signior Gull! are you turn’d filcher of late!
[UK]Dekker Shoemakers’ Holiday IV iv: These two gulles will [...] take master Bridegroome, and mistris Bride napping.
[UK]Return from Parnassus Pt II II v: How say you to the crafty gull.
[UK]Beaumont & Fletcher Honest Man’s Fortune III iii: Didst thou never hear of one Montague, a prodigal gull, that lives about Paris?
[UK]B.E. Dict. Canting Crew n.p.: Gull c. a Cheat.
[UK]New Canting Dict. [as cit. c.1698].
[UK]Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
[UK]C.M. Westmacott Eng. Spy I 161: You’ll excuse me, sir, but as you are fresh, take care to avoid the gulls. [note] Gulls – knowing ones who are always on the look out for freshmen.