Hermes is described as the youngest of the gods in the Homeric Hymn to Hermes.
The hymn presents Hermes as an unusually clever infant who leaves his birthplace on the day of his birth. He immediately begins plotting, inventing the lyre, and stealing Apollo’s cattle. This comic portrayal contrasts with the more formal image of Hermes as the gods’ herald and messenger.
The phrase refers to the literary tradition of the Homeric Hymn, rather than a universally fixed ranking of every Greek deity by age. Greek mythology contains several competing genealogies, and some gods, including primordial beings and Titans, are older than the Olympians.
The Homeric Hymn to Hermes is one of the thirty-three surviving Homeric Hymns. It is especially important because it explains Hermes’ cleverness, mobility, musical invention, and relationship with Apollo.