Meaning

noun a particle that is electrically charged (positive or negative); an atom or molecule or group that has lost or gained one or more electrons

originFrom the ending of anion and cation, which in turn is from Ancient Greek ἰόν (ión, “going”), neuter present participle of εἶμι (eîmi, “I go”). Coined by English polymath William Whewell in 1834 for Michael Faraday, who introduced it later that year.

Etymology from Wiktionary, CC BY-SA 3.0