First recorded as enero in the 13th cent.; earlier 12th cent. Old Spanish yenair. From Vulgar Latin ienuarius 'id.' From Latin ianuarius "January." Composed of Ianus "Janus," the twin-faced god of beginnings and passages (see Jano), and the adjective-forming suffix -arius (see -ero, today a noun-forming suffix).
Portuguese janeiro, Galician xaneiro, Catalan gener, French janvier, Italian gennaio, Aromanian yinar, Romanian ianuarie, Sardinian gennàrgiu