E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Iduna or Idun.
Daughter of the dwarf Svald, and wife of Bragi. She kept in a box the golden apples which the gods tasted as often as they wished to renew their youth. Loki on one occasion stole the box and hid it in a wood; but the gods compelled him to restore it. (Scandinavian mythology.)
Idna seems to personify the year between March and September, when the sun is north of the equator. Her apples indicate fruits generally. Loki carries her off to Giant-Land, when the Sun descends below the equator, and he steals her apples. In time, Iduna makes her escape, in the form of a sparrow, when the Sun again, in March, rises above the equator; and both gods and men rejoice in her return.