His name was commemorated in numerous place-names, such as Lugdunum (Celtic *Lugu
dūnon, "fort of Lugus"; modern Lyon, France), capital of the Roman province of Gallia Lugdunensis. Other such place-names include Lugdunum Clavatum (modern Laon, France) and Luguvalium21
(modern Carlisle, England). It is also possible that Lucus Augusti (modern Lugo in Galicia, Spain) is derived from the theonym Lugus,22
but Lucus in that place may in fact be purely Latin (lucus = 'sacred grove/forest').
Other places which are likely named after him include:
Loudun and Montluçon in France;
Loudoun in Scotland;
Dinlleu in Wales;
Leiden in the Netherlands;
Lugones in Asturias, Spain (territory once inhabited by the Luggones Astur tribe);
Legnica in Silesia;
Lothian in Scotland
Ethnonyms which may derive from Lugus include the Luggones of Asturias,23
and the Lougei, known from inscriptions in Lugo and El Bierzo.19
Lugus was a deity of the Celtic pantheon. His name is rarely directly attested in inscriptions, but his importance can be inferred from place names and ethnonyms, and his nature and attributes are deduced from the distinctive iconography of Gallo-Roman inscriptions to Mercury, who is widely believed to have been identified with Lugus, and from the quasi-mythological narratives involving his later cognates, Welsh Lleu Llaw Gyffes (Lleu of the Skillful Hand) and Irish Lugh Lámhfhada (Lugh of the Long Arm).
In Ireland, Lugh was the victorious youth who defeats the monstrous Balor "of the venomous eye". He was the godly paradigm of priestly kingship, and another of his appellations, lámhfhada “of the long arm”, carries on an ancient Proto-Indo-European image of a noble sovereign expanding his power far and wide. His festival, called Lughnasadh ("Festival of Lugh") in Ireland, was commemorated on 1 August. When the Emperor Augustus inaugurated Lugdunum ("fort of Lugus", now Lyon) as the capital of Roman Gaul in 18 BC, he did so with a ceremony on 1 August (this may be purely coincidental, however). At least two of the ancient Lughnasadh locations, Carmun and Tailtiu, were supposed to enclose the graves of goddesses linked with terrestrial fertility.
Lugus has also been suggested as the origin not only of Lugh and Lleu Llaw Gyffes, but also the Arthurian characters Lancelot and Lot (most famously championed by the Arthurian scholar Roger Sherman Loomis), though more recent Arthurian scholarship has downplayed any such link between Lugus and Lancelot.
The exact etymology of Lugus is unknown and contested. The Proto-Celtic root of the name, *lug-, is generally believed to have been derived from one of several different Proto-Indo-European roots, such as *leug- "black",23
*leuǵ- "to break",4
and *leugʰ- "to swear an oath",5
It was once thought that the root may be derived from Proto-Indo-European *leuk- "to shine", but there are difficulties with this etymology and few modern scholars accept it as being possible (notably because Proto-Indo-European *-k- never produced Proto-Celtic *-g-6