'aprowl' originates from the English prefix 'a-' (from Old English a-, meaning 'on' or 'in') combined with 'prowl' (Middle English 'prowlen'/'prowl'), where 'a-' meant 'on' and 'prowl' meant 'to roam stealthily.'

'aprowl' developed from earlier expressions such as 'a prowl' or 'a-prowling' in Middle and Early Modern English; over time the prefix and noun/verb fused into the single form 'aprowl' used in some dialects and literary contexts.

Initially it meant simply 'on the prowl' or 'in a state of prowling'; that basic sense has largely remained, though the single-word form has become rare and somewhat archaic in modern usage.