'nightcrawler' originates from English, specifically the compound 'night' + 'crawler', where 'night' comes from Old English 'niht' meaning 'night' and 'crawl' (root of 'crawler') comes from Old English 'crēopan' meaning 'to creep'.

'nightcrawler' formed in Modern English as a compound of 'night' (from Old English 'niht') and 'crawler' (from the verb 'crawl', from Old English 'crēopan'); the components passed through Middle English into the modern compound.

Initially it meant 'one who crawls at night' (literal); over time the term broadened to refer to nocturnal animals (notably large earthworms used as bait) and figuratively to people active or prowling at night.