This epithet for Hermes (together with e)riou/nhs) is used already in Homer, Iliad (20.34, 72; 24.360, 440, 457, 679), Odyssey (8.322) and the Homeric Hymns. It is regarded in LSJ as "of uncertain meaning," despite the unanimous judgment of the lexicographic tradition, supported here, that it applies to Hermes as "a great help" (so Hesychius epsilon5871-3; Apollonius, Homeric Lexicon 76.16, 148.17; scholia to Lucian 21.40 Rabe; scholia to Aristophanes, Frogs 1144a-b), because he "strengthens those who worship him" (Cornutus, de natura deorum 21.4). The ancient etymology (Porphyry on Homer, Odyssey 24.1ff.) is from a rare word for "earth," e)/ra (perhaps from an unattested adjective in -ios). It would thus refer to the role of Hermes Chthonios as underworld guide. Its frequent use in Orphic and Hermetic writing may tend to support this explanation. In an epigram of Julian the Egyptian, cited in the Suda (see gamma 456), a doddery old man most likely makes his dedication to Hermes as Eriounios in the hope of the god's help in the afterworld. The second part of the root may be related to the root of o)ni/nhmi, "I help." Less likely is the derivation from e)/rion, "wool," suggested by W.Leaf on Homer, Iliad 20.3.