'anion' originates from New Latin/modern scientific coinage, ultimately from Greek ἀνιῶν (aniōn), the present participle of ἀνίημι (aniēmi) meaning 'to go up' — referring to ions that move toward the anode.

'anion' entered scientific English in the 19th century as electrochemistry terminology developed; it was used to name ions that travel to the anode and contrasted with 'cation' (ions moving to the cathode).

Initially, the term emphasized movement ('going up' toward the anode); over time it came to mean more generally 'a negatively charged ion' regardless of motion.