in ancient Greece or Rome, "herald's staff," 1590s, from Latin caduceus, alteration of Doric Greek karykeion "herald's staff," from kēryx (genitive kērykos) "a herald," probably a Pre-Greek word. Token of a peaceful embassy; originally an olive branch. Later especially the wand carried by Mercury, messenger of the gods, usually represented with two serpents twined round it and wings. Related: Caducean.
The caduceus is a symbol of peace and prosperity, and in modern times figures as a symbol of commerce, Mercury being the god of commerce. The rod represents power; the serpents represent wisdom; and the two wings, diligence and activity. [Century Dictionary]
Sometimes used mistakenly as a symbol of medicine by confusion with the Rod ofAsclepius, Greek god of medicine, which also features a serpent entwined about a rod but only a single serpent.