'wyrm' originates from Old English, specifically the word 'wyrm', where the Proto-Germanic root *wurmiz meant 'serpent, snake, worm'.

'wyrm' changed through Middle English (often spelled 'worm' or 'wyrm') and the sense split: the common modern English 'worm' came to refer mainly to small invertebrates, while the archaic/poetic form 'wyrm' remained for dragon-like creatures and survived in literary and fantasy usage.

Initially, it meant 'serpent, snake, or creeping creature'; over time the general meaning narrowed in common use to 'worm' (small invertebrate), while the archaic form 'wyrm' preserved the older sense of 'dragon' or large serpent.