(someone) Vrb phrs. Essentially meaning the same as 'fuck one's brains out'. Not necessarily intimating anal intercourse. The elements ..the arse off are often added to verbs as a general intensifier, such as bore the arse off. Similarly also see 'bore the pants off'.
FUCK THE ARSE OFF
Meaning of FUCK THE ARSE OFF in English
Slang English vocab. Английский сленговый словарь. 2012