Money. The ribbin runs thick; i.e. there is plenty of money. CANT. Blue ribbin. Gin. The cull lushes the blue ribbin; the silly fellow drinks common gin.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
Ribaldry * To RibroastNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes