A concubine; an allusion to an ancient German custom, according to which, when a man married his concubine, or a woman greatly his inferior, he gave her his left hand.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
leery * legNathan Bailey's 1721 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes