Hermes's image, like Dionysus's, grew younger over time. Archaic herms and early vase paintings show a bearded, dignified figure; by the Classical period sculptors increasingly gave him the athletic, beardless youth familiar from the statue traditionally attributed to Praxiteles at Olympia, showing Hermes cradling the infant Dionysus, an attribution debated by modern scholars but long taken as the model for how the messenger god ought to look, quick and youthful rather than solemn.
In late antique Egypt, Greek settlers identified Hermes with the Egyptian god Thoth, and the fusion produced Hermes Trismegistus, thrice-great Hermes, credited as the author of a body of Greek philosophical and magical writings later called the Corpus Hermeticum. Those texts vanished from Western Europe until Cosimo de' Medici obtained a manuscript and had Marsilio Ficino translate it in the 1460s, ahead even of Ficino's planned translation of Plato, because Cosimo believed Hermes Trismegistus to be an ancient sage older than Moses. The mistaken dating was corrected only in the seventeenth century, but by then the Hermetic corpus had already shaped Renaissance magic, alchemy and philosophy, carrying the boundary-crossing god's name into the whole later Western esoteric tradition this site documents.
Sources The Oxford Classical Dictionary, 4th editionSimon Hornblower, Antony Spawforth and Esther Eidinow (eds.) with Spiritual and Demonic Magic from Ficino to CampanellaD. P. Walker