from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A low bed on casters that can be rolled under another bed for storage.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A low bed, designed to be rolled/stored away, usually on casters, under a higher bed, e.g. for temporary use by guests.
trundle 'pulley' + bed (Wiktionary)