"the Roman god Mercury," mid-12c., from Latin Mercurius "Mercury," originally a god of tradesmen and thieves, from merx "merchandise" (see market (n.)); or perhaps [Klein, Tucker] from Etruscan and influenced by merx. Later he was associated with Greek Hermes. The planet closest to the sun so called in classical Latin (late 14c. in English). A hypothetical inhabitant of the planet was a Mercurean (1855) or a Mercurian (1868). For the metallic element, see mercury.