The Germanic Ethnicity of Isolde, the Goddess Isa and Iceland

In my researches into Germanic mythology I occasionally find references to a rather obscure Germanic Goddess called Isa. Isa as we know is the name of the 11th rune of the Elder Futhark, also known as Is in the Anglo-Saxon Futhork, Iss in the Scandinavian Futharks and Is in the Armanen Futhork.
There is a theory that this Goddess lends her name to Iceland or Island.
"Rassmann identifies Island as derived from Isa, a goddess of the under-world, probably the same as Holda, and not as Iceland."[Legends of the Wagner Drama by Jessie L. Weston]
As a female personal name it is Teutonic and of ancient origin, signifying aristocratic, strong willed, a ruler. The element of strength is brought out in the hard, icey and cold nature of the Isa rune.
It is generally considered that due to the Celtic location and time frame of the Tristan and Isolde legend that Isolde was an Irish Celtic princess. However this is a mistake albeit an understandable one.
During the 9th century CE it was a Viking and not an Irish king that held court in Dublin and we should not forget the significant Scandinavian and thus Germanic heritage of Ireland from the 9th and 10th centuries.
German scholars according to Jessie L. Watson derive Isolde`s name from Iswalt or Iswalda[Eis-walterin=ruler of the ice]. The earliest form of the Isolde name is Isalde[Wolfram von Eschenbach]. Legends always represent her as fair haired-`die lichte` as opposed to the rival dark-haired Isolde. She concludes that the Germanic forms of the name have more in common than the Kymric Essylt.
It is also interesting to consider that in the German Nibelungenlied Brunhild is represented as the queen of Iceland and her very nature is hard, icey and strong-willed. She dwellt in her fortress Isenstein[`Ice rock`]and was a beautiful woman of formidable strength and fortitude.
Could it be that the two distinct legendary figures of Isolde and Brunhild originally derive from a common Germanic source?

*Perkunos-the Original Name of the Northern PIE Thunder God

For a long time I have recognised the special relationship between the Germanic, Baltic and Slavic Thunder Gods, not only in their functions, characteristics and physical attributes but also in the shared etymological origins of His name.
The reconstructed name of the Proto-Indo-European Thunder God is *Perkunos. From this name we derive the name of the Baltic Thunder God Perkonis amongst the Prussians[Prussian is an extinct Baltic language], Perkons from the Latvian and Perkunas from the Lithuanian. All these aforementioned languages are Baltic which is now recognised as the oldest Indo-European language group. I suggest that scholars should direct their efforts in exploring the language, folklore and mythology of the Balts for in so doing we will learn more about our shared Aryan past.
Amongst the Slavic peoples He is named Perun[Czech]and Pyerun[Russian]and Perunu[Old Russian].
There is a possible cognate with the Indic Parjanya, an alternative name for the Hindu God Indra[who is also called Indara amongst the Iranians].
There would not appear to be a direct association with the Germanic Thor/Thunar/Donar but we should recollect that an alternative name for Jord[Thor`s mother] is Fjorgyn which Jaan Puhvel[Comparative Mythology] states is a cognate.
The Celtic Taranis is cognate with the Germanic Thunar and thus indirectly liked to *Perkunos.
All this is suggestive of a very close shared mythological link between the Balts, Slavs and Teutons and a more tenuous link with the Celts. No doubt this is because the Teutons remained as one people with the Balts and Slavs long after the dispersal of the Celts and the link between the Balts and Slavs is much longer still.
These Thunder Gods all carry an axe or a hammer. The Baltic and Slavic Thunder Gods are generally seen with an axe which my readers will know from earlier articles is a much older weapon than the hammer and Thor`s hammer developed from this.
Also the first axes were made of stone and this is reflected in the etymology of hammer which originally meant `stone`.
The antiquity of the northern European Thunder God is also reflected in the Baltic and Slavic names which are derived from PIE *peru which means `stone`.
Amongst our ancestors an association between the Thunder God and the stone axe was made in the concept of thunder falling to earth in the form of a stone axe.
Another thing that these Thunder Gods have in common is their physical and material characteristics-red bearded/red haired, hot-tempered and rambling across the heavens in a chariot pulled by a goat or goats.
The Thunder God amongst the Balts and Slavs is regarded very much as their supreme deity. I believe that at one stage this was also the case amongst the Teutons but as we know in some parts of the Germanic world Thor was still recognised as occupying this position, such as in the north Germanic language area. The cult of Odin/Woden/Wotan appears to have developed in the south Germanic language area and spread northwards.
Amongst the Greek and Roman pantheons the Thunder God[Zeus/Jupiter] still reigned as supreme which is an indication of His great antiquity and importance.
Within the Germanic heathen community we need to give proper recognition to the Thunder God and not shy away from exploring the myths, folk tales and folklore of related northern Aryan peoples and indeed other non-Indo-European speaking peoples such as the Finns for it would appear that Finnish mythology has much in common with Germanic mythology.
The Finnish Thunder God is Ukko, whose sacred trees are the oak and the rowan and His weapon is an axe or a hammer, sometimes a stick or a sword. It is believed that He has Indo-European origins. Iron age specimens of axe and hammer pendants have been found in Finland. His name may have developed from Perkele which seems suspiciously related to *Perkunos.

Sources: Comparative Mythology by Jaan Puhvel.
The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World by J.P. Mallory and D.Q. Adams.
European Myth and Legend by Mike Dixon-Kennedy.