Green’s Dictionary of Slang

gerver n.

[var./mispron. of gopher n.2 (3)]

(US Und.) a safe breaker.

[US]J. Sullivan ‘Criminal Sl.’ in Amer. Law Rev. LII (1918) 890: A safe blower is called a gopher man, Peter man or yeggman and ‘Gerver.’.
[US]G. Henderson Keys to Crookdom 406: Gerver. Safe-cracker.