Jacob Grimm in Teutonic Mythology Volume I makes a comparison between Woden and the British deity Gwydion in his footnotes on page 150, Chapter VII (Wuotan, Wodan [Odinn]:
"In the Old British mythology there appears a Gwydion ab Don, G. son of Don, whom Davies (Celtic Researches pp. 168, 174. Brit.myth.p 118,204,263-4,353,429.504,541) identifies with Hermes; he invented writing, practised magic, and built the rainbow; the milky way was named caer Gwydion, G.'s castle (Owen, sub v.). The British antiquaries say nothing of Woden, yet Gwydion seems near of kin to the above Gwodan=Wodan. So the Irish name for dies Mercurii, dia Geden, whether modelled on the Engl. Wednesday or not, leads us to the form Goden, Gwoden (see Suppl.)"
It is interesting that according to Paul the Deacon (8th century CE) amongst the East Germanic tribes of the Vandals and Langobards Wodan was referred to as Godan or Guodan. Indeed the subsitution of the 'w' for a 'g' is to be found in other places in the Germanic world. Grimm refers to places which were sacred to Wodan which contain the initial letter 'g' such as Godesberg, near Bonn which in the Middle Ages was called Gudensberg. Indeed the older name of the city was Wodenesberg. Near the holy oak at Hesse there was a Wuodenesberg which has variously been called Vdenesberg and Gudensberg. There is also a Gudensberg near Erkshausen in Rotenburg and likewise a Gudensberg near Oberelsungen and Zierenberg. The Latin spelling would be Vodinberg. There is also a city referred to in mediaeval documents called Gotansberg. So there certainly seems to be a precendent in the Germanic world for connecting Wodan with Godan.
Returning to the subject of Gwydion being Woden Charles Squire in The Mythology of the British Islands states:
"It was a belief common to the Aryan races that wisdom as well as wealth came originally from the underworld; and we find Math represented in the Mabinogi bearing his name as handing on his magical lore to his nephew and pupil Gwydion, who there is good reason to believe was the same divine personage whom the Teutonic tribes worshipped as 'Woden' and 'Odin'. Thus equipped Gwydion son of Don became the druid of the gods, the 'master of illusion and phantasy', and not only that but the teacher of all that is useful and good, the friend and helper of mankind, and the perpetual fighter against niggardly underworld powers for the good gifts which they refused to allow out of their keeping."
We already have seen from earlier articles that Woden/Loki equate with the Celtic Lugos/Lugh/Lleu and yet the Mabinogi of Math makes it clear that Gwydion fathered Lleu through His sister Arianrod (Aryan Wheel). He is thus His own father just as Widar is both the son of Woden and Woden reborn. I do recommend Squire's work which incidentally was also studied by Savitri Devi no less!
Robert Graves in his The White Goddess states:
"Professor Sir John Rhys takes Gwydion for a mixed Teuton-Celt deity and equates him with Woden...." (page 51)
Also: "That the Belgae invaded Britain in 400 BC, and that their god was the [Celto-Teutonic] Gwydion [alias Woden, or Odin] and that the ash [Ygdrasill] was sacred to him." (Appendix A Two Letters to the Press)
It is interesting that Graves should identify the Belgae who invaded Britain as a Teutonic tribe. This is something which I have discussed in a earlier post concerning the colonisation of Britain by Germanic peoples much earlier than the accepted date of 449 CE. See: http://celto-germanic.blogspot.co.uk/2012/06/ancient-presence-of-germanic-peoples-in.html
See also: http://celto-germanic.blogspot.co.uk/2013/04/the-belgae-and-ancient-germanic.html