Green’s Dictionary of Slang

a young thief.

1846		G.M. Reynolds ‘Thieves’ Alphabet’ in Mysteries of London I 60/1: Z was a Ziff* [*Juvenile thief] who was flashed on the horse.* [*Privately whipped in prison].
1864, 1867, 1870		Hotten Sl. Dict.
1873		Sl. Dict.
1890–1904		Farmer & Henley Sl. and Its Analogues.
1895		Crowe Aus. Sl. Dict. 98: Ziff, a young thief.