Beli Mawr: Welsh God of Light (?) also called Beli, Belin, Belinos, Belinus, Bellinus, Belenos, and in Ireland called Bile

beli: shining (modern Welsh: pelydur--radiant. It is common for b's and p's to mutate into one another in Welsh, depending on dialect and time period. Deriving from the Celtic word bel--to shine, to be bright. The old Celtic god was called Belinos/Belenos)
mawr: great

Legendary king of Britain, Beli is in origin a Celtic sun god, consort to the earth mother Don. His feast day was called "Beltane"--"Fire of Bel" or "Bright Fire." He is primarily a god of light and therapy, equated with Apollo.

Later legend makes him king of Britain. Some sources make him brother to Cunobelinus (Cymbeline), whose name, by the way, means "Hound of Beli." Elsewhere, (namely in The History of the Kings of Britain), he is made the brother of Brennius (Bran), and his rival. This rivalry may be a half-rememberence of the battles between the Children of Don and the Children of Llyr, as Bran was the son of Llyr, and Beli the consort of Don.

He is also associated with Cernunnos by way of a statue depicting him with horns and calling him Mars Belatucadros, or "Mars the Shining One". This was found in Cumbria. In Ireland, where he is called Bile or Bíle, he is also a god of death and the underworld. As unlikely as this may seem, remember that the Celts believed in reincarnation and at one point had a solar cult. The belief in a dying and rising god is not so far-fetched.

He is also thought, by Roger Sherman Loomis, to be the origin of the Arthurian figure of Pellinor, father of Percivale (Perceval). Again, the mutation of B to P and (here) M to N makes the case: Beli Mawr--> Pelli Nor--> Pellinor.