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.
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.
<a href="https://www.etymonline.com/word/Athenian">Etymology of Athenian by etymonline</a>
Harper, D. (n.d.). Etymology of Athenian. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/Athenian