Worms was a name for the race of Dragons, and especially those wingless kinds (such as Glaurung himself) who crawled on the ground.
Worm is an actual old word for dragon, derived from Old English wyrm, Old Norse ormr ("serpent").
- ↑ J.R.R. Tolkien; Verlyn Flieger, Douglas A. Anderson (eds.), Tolkien On Fairy-stories: Expanded edition, with commentary and notes, p. 108