mercury [OE] Mercury was the Roman god of eloquence, skill, trading, and thieving, and was the messenger of the gods. His name came from Latin merx ‘merchandise’, the source also of market [OE], merchant [ME], and mercenary [LME]. In later Latin mercurius was also the name of a silvery-white metal, liquid at room temperature. The use probably arose from the fluidity of the metal being likened to the rapid motion associated with the god. In English the metallic element was first called mercury in the Middle Ages—its earlier name was quicksilver (see quick).