Green’s Dictionary of Slang

mosh v.1

[mooch v.]

1. to leave a restaurant without paying one’s bill; thus the mosh n., the practice of committing this fraud.

1857
18601870188018901900
a.1904
[UK]‘Ducange Anglicus’ Vulgar Tongue 22: ‘Doing the mosh on the quiet.’ Dining at an eating-house, and not paying.
[US]Matsell Vocabulum.
[UK]Farmer & Henley Sl. and Its Analogues.

2. to pawn.

1923
1923192419251926192719281929
1930
[UK]J. Manchon Le Slang.
[US](con. 1910–20s) D. Mackenzie Hell’s Kitchen 119: Mosh ... to pawn.

In compounds