annelid n.

"inferior opening of the alimentary canal," 1650s, from Old French anus, from Latin anus "ring, anus," from PIE root *āno- "ring." So called for its shape; compare Greek daktylios "anus," literally "ring (for the finger)," from daktylos "finger."

word-forming element meaning "like, like that of, thing like a ______," from Latinized form of Greek -oeidēs (three syllables), from eidos "form," related to idein "to see," eidenai "to know;" literally "to see" (from PIE *weid-es-, from root *weid- "to see"). The -o- is connective or a stem vowel from the previous element. Often implying an incomplete or imperfect resemblance to the thing indicated.