CHUB,
He is a young Chub, or a meer Chub, very ignorant or unexperienc'd in Gaming, not at all acquainted with Sharping. A good Chub, said by the Butchers, when they have bit a silly raw Customer.
Chub in the 1811 Vulgar Tongue
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).