Green’s Dictionary of Slang

(Aus.) a handyman who works for a prostitute; thus derog. phr. he couldn’t get a job as a bumper-upper in a brothel.

1950		‘No. 35’ Argot in G. Simes DAUS (1993) 31/1: bump up (v intr) To urge someone to take a particular course of action; hence bumper-upper, an urger. ‘He couldn’t get a job as a bumper-upper in a brothel’, to indicate the nadir of futile incompetence.
1955		‘No. 35’ Argot in G. Simes DAUS (1993) 31/1: To act as an accomplice to a thief by bumping a victim, and so distracting his attention [...] Usually the learner or the weak sister is the bumper-upper. If a bloke is a no-hoper, it may be said of him ‘He couldn’t get a job as a bumper-upper in a brothel.’.