Phrases and idioms:
acorn barnacle a multivalve marine cirriped, Balanus balanoides, living on rocks. acorn worm any marine wormlike animal of the phylum Hemichordata, having a proboscis and gill slits, and inhabiting seashores.
Etymology: OE aeligcern, rel. to aeligcer ACRE, later assoc. with OAK and CORN(1)
Useful english dictionary. 2012.