A small Indian coin, mentioned in the Gentoo code of laws: hence etymologists may, if they please, derive the common expression, I do not care a dam, i.e. I do not care half a farthing for it.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Daisy Kickers * DamberNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes