The story
- Old English · inherited fromtrēowwyrm“tree-worm, palmerworm”
- Middle English · inherited fromtree worme
- English todaytree worm
From Middle English tree worme, tre-worme, treworme, from Old English trēowwyrm (“tree-worm, palmerworm”), equivalent to tree + worm.
Etymology from Wiktionary, CC BY-SA 4.0.