Green’s Dictionary of Slang

mutcher n.

[var. on moocher n. (1)]

a thief who steals from drunks.

[UK](con. 1840s–50s) H. Mayhew London Labour and London Poor IV 282/1: They loiter about the streets and public-houses to steal from drunken persons, and are called ‘Bug-hunters’ and ‘mutchers’.