1520s, "native or inhabitant of Athens;" see Athens + -ian. From 1580s as an adjective, "pertaining to Athens." Old English had Atheniense (plural noun), from Latin Atheniensis.
Entries linking to athenian
Athens
city of ancient Attica, capital of modern Greece, from Greek Athenai (plural because the city had several distinct parts), traditionally derived from Athena, but probably assimilated from a lost name in a pre-Hellenic language.
-ian
variant of suffix -an (q.v.), with connective -i-. From Latin -ianus, in which the -i- originally was from the stem of the word being attached but later came to be felt as connective. In Middle English frequently it was -ien, via French.