Gaulish Mercury is associated with triplism: sometimes he has three faces, sometimes three phalluses, which may explain the plural dedications. This also compares with Irish myth. In some versions of the story Lug was born as one of triplets, and his father, Cian (“Distance”), is often mentioned in the same breath as his brothers CĂș (“Hound”) and Cethen (meaning unknown), who nonetheless have no stories of their own.

Source: Lugus – Wikipedia