Etymology: < (i) Middle French ionique, ionicque, jonique, yonicque (Middle French, French ionique ), adjective (1375 in extended sense ‘Greek’, c1400 designating the language of the Ionians, 1476 designating a metre, a1537 designating one of the Greek orders of architecture) and noun (1586 denoting the Ionian mode), and its etymon (ii) classical Latin Iōnicus of or belonging to Ionia, Ionian, specifically designating a Greek dialect, a literary style, or a metrical foot < ancient Greek Ἰωνικός of, relating to, or characteristic of the Ionians or their language, Ionian, belonging to the Ionian order of architecture, in Hellenistic Greek also specifically designating a Greek dialect, a literary style, or a metrical foot < Ἰωνία Ionia (see Ionian adj.²) + -ικός -ic suffix. Compare Spanish ionico (second half of the 15th cent.), Italian ionico (1436, earliest in sense A. 2). With use as noun compare classical Latin Iōnicus (masculine), Iōnicum (neuter), denoting a kind of dance, Iōnicon (neuter), denoting a metrical foot, Hellenistic Greek Ἰωνικοί (plural) inhabitants of Ionia. Compare later Ionian n.¹, Ionian adj.², Ionical adj.¹Compare the following contextual borrowing of post-classical Latin Ionice, adverb (1503 or earlier), with reference to the Ionic dialect of ancient Greek:1565 J. Jewel Replie Hardinges Answeare iii. 164 But what if S. Luke had saide, they spake Ionicè, Aeolicè, or Doricè,..would he therefore conclude, they spake no Greeke?

Etymology: < ion n. + -ic suffix.