MERCURY (Gr. ̔Ερμη̂ς, G2258. RSV HERMES, hěr’-mēz, Acts 14:12). Greek and Roman demigod, son of Zeus and Maia.
Mercury was cunning from birth; e.g., he invented the lyre on the day he was born. He performed many functions: he was the guide of souls from earth to Hades; he was the patron of merchants and travelers, including robbers; and was associated with fertility. He is chiefly represented, however, as messenger of the gods, and is represented as a herald, with cap, sandals, and the caduceus or herald’s staff. It is this role that prompted the people of Lystra to call Paul Mercury (Hermes), since he seemed to be the spokesman for himself and Barnabas (Acts 14:12), who were believed to be gods after performing the miracle of healing on the lame man.
International Standard Bible Encyclopedia (1915)
mur’-ku-ri, mer-ku’ri-us: The translation of Hermes, in Ac 14:12: "They called Barnabas, Jupiter; and Paul, Mercury, because he was the chief speaker." Hermes was the god of eloquence (and also of theft), the attendant, messenger and spokesman of the gods. The more commanding presence of Barnabas (compare 2Co 10:10) probably caused him to be identified with Zeus (the Roman Jupiter), while his gift of eloquence suggested the identification of Paul with Hermes (the Roman Mercury). The temple of Jupiter was before Lystra, and to him the Lycaonians paid their chief worship. Compare the legend of Baucis and Philemon (Ovid, Metam. viii.611 f).
See Hermes; Jupiter; GREECE, RELIGION IN ANCIENT.