Learned borrowing from Ancient Greek ἀνιόν (anión, “(thing) going up”), neuter present participle of ἄνειμι (áneimi, “go up”), from ἀνά (aná, “up”) + εἶμι (eîmi, “go”). Coined by English polymath William Whewell in 1834 for Michael Faraday, who introduced it later that year. By surface analysis, an- (“up, away, forward”) + ion.