Lug is the Old Irish form of Lugh, a name deeply rooted in Celtic mythology and linguistic reconstruction. Derived from Primitive Irish Luga, which itself traces back to Proto-Celtic *Lugus, the name ultimately connects to a pan-Celtic deity whose attributes and worship spanned the ancient Celtic world. In Old Irish, Lug appears primarily in mythological contexts, where the name is historically genitive Loga (e.g., Lugnasad 'the assembly of Lug'). The name gradually evolved in Irish: the form Lú is used in Modern Irish, while Lugh, a later spelling, is often employed in English-language references to Irish mythology. Beyond Ireland, the name is cognate with Lleu in Welsh mythology and Lugus, a Gaulish god equated with the Roman Mercury. The god Lugus was associated with commerce, craftsmanship, and possibly light—his name may be derived from a root meaning 'light' or 'brightness', though alternative etymologies connect it to 'darkness' or 'oath'. The spread of the name across Insular and Continental Celtic cultures testifies to its significance in the pre-Christian Celtic pantheon. Lug is also attested in German as a rare noun meaning 'falsehood' (often used in the phrase Lug und Trug 'lies and deceit'), from the verb lügen 'to lie'. This Germanic word, however, is etymologically unrelated to the Gaelic mythological name. Although Lug is rarely used as a given name in modern times due to its strong mythological associations, it appears in modern English as an alternative spelling of Lugh. Notable bearers are exclusively mythological, especially as a figure in the Ulster Cycle where Lug (often called Lugh in English) is a key member of the Tuatha Dé Danann and father of the hero Cú Chulainn. Key facts Meaning: Possibly 'light' or 'brightness', from Proto-Celtic *Lugus Usage: Irish (historical); also English as an alternate spelling of Lugh Origin: Old Irish form of the mythological god Lugh/Lugus Related names: Lugh, Lú, Lugus, Lleu