MERCURY. - An ancient Roman divinity, who appears in the first lists of the twelve gods. The very name of Mercurius (from *merv*, *mercari*) clearly explains the original figure of the god—as protector of commerce—whose cult was fostered not only by Rome’s relations with Cumae and Sicily, but especially when the *Hermes Emporios* (i.e., Hermes [v.], protector of merchants) entered Rome, whose other qualities were also assimilated.
Mercury was especially venerated by merchants, who celebrated his festival on May 15 (*feriae Iovi Mercurio Maiae*), which coincided with the anniversary of the dedication of his temple, erected in 495 B.C. near the Circus Maximus. In the same year of the dedication, according to tradition (Livy, V, 13, 6), the public *annona* was organized and a special guild (collegia, which later spread widely in Italy and beyond) of merchants was established, called *mercatores* or *mercuriales*, having their seat within the *pomerium*. On the Ides of May, they were accustomed to sprinkle themselves with laurel sprigs dipped in the *fons Mercurii*, near Porta Capena (not far from the temple), praying the god to “wash” them of the lies told in the adjacent forums in the exercise of their trade (Ovid, *Fasti*, V, 670 ff.). The effigy of Mercury first appears on the heavy bronze coinage of the mid-4th century, clearly an imitation of the Greek Hermes: youthful, beardless face, petasus adorned with two small wings.
Altheim, however, holds that the name Mercurius was originally the name of a *gens Mercuria*, of which Hermes would have been the clan god in Etruria, and that both Mercury and the Greek god were later introduced into Rome by the Etruscans themselves.
Cesare D’Onofrio