Hermes/Mercury was originally a god of the flock. Because at that time wealth was measured in sheep, he became the god of prosperity, and as the culture became more sophisticated, the god of commerce and all its associative skills and concerns: travel, messages, persuasive speech, prudence, shrewdness, and luck. By the Classical period, his role had blossomed. He became the god of wisdom, magic, oratory, writing, skill, and trickery; the messenger of Zeus; and as the guide to the souls of the dead, the "Psychopomp", the ultimate god of travel. Of all the Roman gods, the Celts identified the most with Mercury. They amalgamated him with their local deities to form Mercury Arvernus, Mercury Artaios, and many others. As was common with Celtic deities, he was given a female consort. Her name was Rosmerta. In Ireland he was equated with the god Lugh.
In Helenistic Egypt, Hermes was equated with the Egyptian god Thoth, to become Hermes Trismegistus - the thrice great Hermes. In ancient Alexandria philosophers and mystics signed his name to their writings to give him credit as the source of their wisdom. These Hermetic texts are at the root of Western alchemy, magic, and mysticism.
His winged sandal, the "talarius", was the symbol of his swiftness, as he fulfilled his role as messenger and as protector of travelers and athletes. His winged hat was called a "petasus", a traveler's hat. Its symbolism was the same as the talarius, but it additionally became the symbol of inspiration, because as psychopomp, he was likewise the guide of the mystic. His herald's staff, the "caduceus," was a magic wand that could change lead into gold and cure any illness; therefore it became the symbol of modern medicine. (The Alchemic Egg)