Green’s Dictionary of Slang

1. (US Und.) a thief; thus stone-getter, a diamond thief.

1512		Hickscorner Avii: Braulers lyers getters and chyders Walkers by nyght with grete murderers [...] and Joly carders Oppressers of people with many swerers.
1906		A.H. Lewis Confessions of a Detective 8: My ability to successfully cope with a fan-tan den in Doyer Street, or pinch a poke-getter at the Ferry.
1920		Ade Hand-made Fables 186: Once there was a Getter named Ichabod Roxworthy.

2. (UK Und.) a criminal who steals letters for forgery gangs.

1941

V. Davis Phenomena in Crime 48: Reign of ‘getter’ [...] nine months.