A little child. Kinchin coes; orphan beggar boys, educated in thieving. Kinchin morts; young girls under the like circumstances and training. Kinchin morts, or coes in slates; beggars’ children carried at their mother’s backs in sheets. Kinchin cove; a little man. Cant.
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.
To Kimbaw * King’s PlateNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes