English Meaning: The name Oona is an English baby name. In English the meaning of the name Oona is: One. Latin Meaning: The name Oona is a Latin baby name. In Latin the meaning of the name Oona is: One. Irish Meaning: The name Oona is an Irish baby name.In Irish the meaning of the name Oona is: Lamb.Can also be an IrishUna: One.n English the meaning of the name Oona is: One. Latin Meaning: The name Oona is a Latin baby name. In Latin the meaning of the name Oona is: One. Irish Meaning: The name Oona is an Irish baby name. In Irish the meaning of the name Oona is: Lamb. Can also be an IrishUna: One.