Green’s Dictionary of Slang

(UK Und.) the lookout man for a team of thieves who steal by hooking objects from stalls or shop windows.

1591		Greene Second Part of Conny-Catching in Grosart (1881–3) X 122: Then streight he sets the Warp to watch, who hath long cloak to couer whatsoeuer he gets.
1608		Dekker Belman of London G: He that hookes is called the Curber. He that plays the spy is the Warpes.
1630		J. Taylor ‘A Brood of Cormorants’ in Works (1869) III 8: Liues like a Gentleman by sleight of hand, / Can play the Foist, the Nip, the Stale, the Stand, / The Snap, the Curb, the Crossbite, Warpe and Lift, / Decoy, prig, Cheat (all for a hanging shift).