'ionic' (relating to ions) originates from New Latin/modern scientific coinage based on Greek 'ion' (ἰόν), where 'ion' meant 'going' (from the verb 'ienai', 'to go'); the adjectival suffix '-ic' was added in modern scientific formation. Separately, 'Ionic' (capitalized) for the architectural order derives from Greek 'Ionikos' meaning 'of Ionia' (a region of Anatolia).

'ionic' (chemical sense) was formed in the 19th century after Michael Faraday's coinage of 'ion' (from Greek) to name charged particles, producing English adjective 'ionic'. The architectural sense comes much earlier from classical Latin/Greek ('Ionikos') and entered English to name the 'Ionic order' of classical architecture.

Initially, the Greek root 'ion' literally suggested 'that which goes' (from 'to go'); in the 19th century it was repurposed for charged particles and later extended to adjectives like 'ionic' meaning 'relating to ions'. The separate architectural sense originally meant 'of Ionia' and has retained that specific historical meaning in references to the Ionic order.