In Norse mythology , the goddess IÃ unn gives apples to the gods in Prose Edda ( written in the 13th century by Snorri Sturluson ) that makes them young forever . In Norse mythology , the goddess IÃ unn is portrayed in the Prose Edda ( written in the 13th century by Snorri Sturluson ) as providing apples to the gods that give them eternal youthfulness .