Ian

masc. proper name, Middle English Jon, Jan (mid-12c.), from Old French Jan, Jean, Jehan (Modern French Jean), from Medieval Latin Johannes, an alteration of Late Latin Joannes, from Greek Ioannes, from Hebrew Yohanan (longer form y'hohanan), said to mean literally "Jehovah has favored" or "Jah is gracious," from hanan "he was gracious."

Greek conformed the Hebrew ending to its own customs. The -h- in English was inserted in imitation of the Medieval Latin form. Old English had the Biblical name as Iohannes. As the name of John the Baptist and John the Evangelist, it was one of the most frequent Christian given names, and in England by early 14c. it rivaled William in popularity and was used generically (in Middle English especially of priests) and as an appellative (as in John Barleycorn, John Bull, John Q. Public). Somehow it also became the characteristic name of a Chinaman (1818).

The Latin name also is the source of French Jean, Spanish Juan, Italian Giovanni, Portuguese João, also Dutch Jan, Hans, German Johann, Russian Ivan. Welsh form was Ieuan, Efan (see Evan), but Ioan was adopted for the Welsh Authorized Version of the Bible, hence frequency of Jones as a Welsh surname.