'arsle' originates from Old English, specifically from words like 'ærs' (Old English) and the Proto-Germanic root '*arsaz', meaning 'buttock'.

'arsle' developed as a regional/dialectal variant from Middle English forms such as 'arse', 'arsel' and related spellings; the Scots and northern English dialect form 'arsle' preserves this variant spelling and pronunciation.

Initially it meant 'buttock' (the physical posterior), but over time the word also came to be used as a vulgar insult meaning 'a contemptible or foolish person'.