'arrowworm' originates from Modern English as a compound of the words 'arrow' (from Old English 'earh', meaning 'a projectile for shooting') and 'worm' (from Old English 'wyrm', meaning 'serpent, worm'), formed to describe a worm with an arrowlike shape.

'arrowworm' first appeared in English as the hyphenated or compounded form 'arrow-worm' in the 19th century to name members of the phylum Chaetognatha; over time the hyphen was often dropped, giving the modern single-word form 'arrowworm'.

Initially, the compound simply described a 'worm shaped like an arrow'; over time it became a standard common name specifically for chaetognath worms, retaining the sense of arrowlike shape but gaining taxonomic reference.