1590s, from Latin caduceus, alteration of Doric Greek karykeion "herald's staff," from karyx (genitive karykos) "a herald," from PIE *karu-, from root *kar- "to praise loudly, extol" (cognates: Sanskrit carkarti "mentions with praise," Old English hreð "fame, glory"). Token of a peaceful embassy; originally an olive branch. Especially the wand carried by Mercury, messenger of the gods, usually represented with two serpents twined round it.