Page "Mercury (mythology)" Paragraph 8

When they described the gods of Celtic and Germanic tribes, rather than considering them separate deities, the Romans interpreted them as local manifestations or aspects of their own gods, a cultural trait called the interpretatio Romana.

Mercury in particular was reported as becoming extremely popular among the nations the Roman Empire conquered ; Julius Caesar wrote of Mercury being the most popular god in Britain and Gaul, regarded as the inventor of all the arts.

This is probably because in the Roman syncretism, Mercury was equated with the Celtic god Lugus, and in this aspect was commonly accompanied by the Celtic goddess Rosmerta.

Although Lugus may originally have been a deity of light or the sun ( though this is disputed ), similar to the Roman Apollo, his importance as a god of trade made him more comparable to Mercury, and Apollo was instead equated with the Celtic deity Belenus.