Dictionary.net

• kin'chin, n. a child in thieves' slang.--n. KIN'CHIN-MORT, a child, generally a girl.--KINCHIN LAY, the robbing of children. [Cf. kidnap.]

1908 - Chambers's Twentieth Century Dictionary of the English Language
By Thomas Davidson

• (cant.). Child; k. lay, practice of stealing money from children sent on errands. [Greek]

1919 - The concise Oxford dictionary of current English
By Sir Augustus Henry