Meaning

adjective having no known name or identity or known source

adjective not known or lacking marked individuality

originBorrowed into English around 1600 from Late Latin anonymus, from Ancient Greek ᾰ̓νώνῠμος (ănṓnŭmos, “without name”), from ᾰ̓ν- (ăn-, “un-”) with ὄνῠμᾰ (ónŭmă), Aeolic and Doric dialectal form of ὄνομᾰ (ónomă, “name”). English equivalent anonym + -ous, its full etymology being an- + -onym + -ous.

Etymology from Wiktionary, CC BY-SA 3.0