Green’s Dictionary of Slang

1. (US, also crumb up) [crum n. (1)] to boil one’s clothes to get rid of the lice.

1926		N. Klein ‘Hobo Lingo’ in AS I:12 650: Crum-up — washing one’s under clothing.
1930		‘Dean Stiff’ Milk and Honey Route 203: Crum up – Same as boil up.
1950		Goldin et al. DAUL 53/2: Crumb up. To boil or otherwise disinfect, as verminous clothing.
1964		(con. 1920s–40s) in J.L. Kornbluh Rebel Voices.

2. see crumb up v.¹