KINCHIN-Morts,
Girls of a Year or two old, whom the Morts (their Mothers) carry at their Backs in Slates (Sheets) and if they have no Children of thir own, they borrow or steal them from others.
The Vulgar Tongue originally collected by Grose, 1811.
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).