COD,
a good Sum of Money; also a Fool. A meer Cod, a silly, shallow Fellow. A rum Cod; a good round Sum of Money. An honest Cod; a trusty Friend.
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Entry taken from 1736 Canting Dictionary, by Nathan Bailey.
Cod in the 1811 Vulgar Tongue
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).