caduceus n.

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," which is probably a Pre-Greek word. A token of a peaceful embassy, it was originally an olive branch. Later especially it was 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]

The word and the thing are 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.