Gender Feminine Usage Greek Mythology Scripts Ἰώ(Ancient Greek) Pronounced Pron. /iː.ɔ̌ː/(Classical Greek) /ˈaɪ.oʊ/(English) Meaning & History Meaning unknown. In Greek mythology Io was a princess loved by Zeus, who changed her into a heifer in order to hide her from Hera. A moon of Jupiter bears this name in her honour.