A sheriff's officer, who arrests debtors; so called perhaps from following his prey, and being at their bums, or, as the vulgar phrase is, hard at their a-ses. Blackstone says, it is a corruption of bound bailiff, from their being obliged to give bond for their good behaviour.
BUM BAILIFF
Meaning of BUM BAILIFF in English
Slang English vocab. Английский сленговый словарь. 2012