TEYRNON TWRF LLIANT

Poseidon

From the beginning of my new book THE BEAR KING:

There is, however, some evidence in the Taliesin poetry suggesting that while Uther does seem to originate from the mil uathmar/fer uathmar of the Irish "Conception of Mongan" tale, another parallel tradition existed which actually identified him with that story's Manannan son of Lir.

Several scholars (including Rachel Bromwich) call attention to the fact that the Cawrnur in the 'Marwnat Vthyr Pen' or "Death-Song of Uther Pen[dragon]" is also mentioned in the Taliesin poem entitled 'Cadair Teyrnon', "The Chair of the Divine Lord." In this latter poem, it would appear Teyrnon (whose name matches that of the MABINOGION hero Teyrnon Twrf Lliant, 'Divine Lord of the Roaring Sea') is involved in a horse raid on Carwnur and his sons.  As it happens, Arthur is also prominently mentioned in the 'Cadair Teyrnon'.  This has led some (like Thomas Green in his ARTHURIANA: EARLY ARTHURIAN TRADITION AND THE ORIGINS OF THE LEGEND) to wrongly assume that the Teyrnon in question is actually Arthur.

I would make the case instead for Teyrnon in the 'Cadair Teyrnon' being Manawydan (= in this context, Manannan the father of Mongan, who transformed into Fiachra in order to lie with Fiachra's queen). The twrf lliant sobriquet of Teyrnon, meaning ‘roaring sea’ or the like, is equivalent to epithets used for Poseidon/Neptune (cf. Greek Alídoupos, ‘sea-resounding’).  This Classical god is constantly linked to the roaring waters of the ocean.  In Classical sources, Neptune is referred to as dominus ("lord"; e.g. Seneca) and even as tyrannus (Ovid).  Welsh teyrn, the root of Teyrnon, is cognate with Latin tyrannus.

Poseidon (as Hippios; cf. Neptune Equestris)) was also the god of horses, which is why he would be paired with Rhiannon or Epona Regina. In fact, I would go so far as to also equate Pwyll with Manawydan, as the former is merely the Welsh word meaning, according to the Geiriadur Prifysgol Cymru, “deliberation, consideration, care, caution; discretion, prudence, wisdom, patience, understanding, intelligence, perception, judgement, mind, wit(s), reason, (common) sense, sanity.” These characteristics perfectly describe the personality of Manawydan as he appears in the MABINOGION.  So as Pryderi (the word for care, anxiety, etc.) is merely a nickname for Gwri/Gwair/Gwarae, a borrowing of Irish guaire, ‘hair of an animal or bristles’, so is Pwyll a byname for Manawydan.

[Gwri Gwallt Eurin or ‘Golden Hair’ is exchanged for a colt at birth.  In other words, like his mother and father he could assume horse form. According to Whitley Stokes in ON THE METRICAL GLOSSARIES OF THE MEDIEVAL IRISH, guaire could mean ‘folt fionn’, ‘fair/yellow hair.’]

Llantarnam, from an earlier Nant Teyrnon, near Caerleon, preserves the god's name.  As was often the case, what was once a pagan sanctuary became a Christian church and then a monastery.  A St. Deuma is associated with the place.  This name is from Irish Diuma, according to O Corrain and Maguire's IRISH NAMES a pet-form of Diarmait.  This is interesting in so far as there was a famous 6th century Irish king named Diarmait, often said to be the last pagan ruler of the country.  A story has come down to us about his dealings with another king, Aedh GUAIRE.

What we have in Uther, then, is a conflation of two characters from the "Conception of Mongan": the mil uathmar (a character created as an eponym for Degsastan as Egesan stan) and Manannan mac Lir.

Neither were the father of Arthur.