Thrasi may be named after Trassach. See the Uí Bairrche.
The Book of Settlements is a medieval Icelandic written work which describes in the settlement (landnám) of Iceland by the Norse in the 9th and 10th centuries.
Part IV Chapter V.
Lomund and Thrasi agree that Jokul’s-river shall divide the East and South Quarters.
Then when Lodmund was old, Thrasi dwelt at Skogar; he was skilled in the art of magic ; it happened once upon a time that Thrasi saw one morning a great rushing forth of waters and with his magic power he turned the waters to the east of Solheimar. Then a thrall of Lodmund's saw this and said that the sea was rushing upon them from the north of the land. Lodmund was then blind ; he bade the servant bring him in a bilge water tub what he called the sea, and when he brought it Lodmund said, " that does not seem to me to be sea water " ; then he bade the thrall guide him to the water, '' and stick thou my staffspike," he said, "into the water": and Lodmund held the staff clasped with his two hands, biting the ring in it at the same time ; then the waters began to flow to the westward beyond Skogar again ; and in this manner each would lead the waters away from himself, until they met at certain gorges, where they made peace on the terms that the river should run there where the way was shortest to the sea ; it is now called Jokul’s river and parts the Quarters of the land.
Part V Chapter I.
Thrasi settles between Kaldaklof-river and Jokul’s-river, Hrafn the Foolish settles between Kaldaklof-river and Lambfell-river.
There was a man named Thrasi, the son of Thorolf Hornbreaker, he went from Hordaland to Iceland and took land between Kaldaklof-river and Jokul's-river; he abode at Skogar the easternmost; he was a man of exceeding great strength, and had quarrels with Lodmund the Old as is written before. The son of Thrasi was Geirmund, the father of Thorbjorn, the father of Brand of Skorgar.
Ref: The Book of Settlements: Landnámabók
The first settler at Skogar was Thrasi son of Thorolfsson. He was a learned man and his character was antiquated. He is said to have hidden a chest filled with gold coins in a cave behind the waterfall. On fine days, when the sun is shining, people say that his gold is glittering through the water. Many have tried to find the chest and once a young man succeeded. He tied a rope to its ring and pulled. He only retrieved the ring, which was later used for the church door at Skogar. Now it is one of the prides of the Skogar Museum.
The Skogar-foss, force or waterfall, yonder, falling sheer over the rock cliffs into the sea, gently sways to and fro in the wind. It falls from so great a height that it appears to lose itself in vapour or dust, like the Staubach. There is an old tradition that an early colonist, Thrasi, before dying, buried a chest of gold and jewels in the deep rock-basin into which this magnificent sheet of water tumbles.
Mr. Brynjúlfsson had the following lines—intimating the hopelessness of searching for the treasure concealed below—repeated to him, when recently visiting the locality. They are thus literally rendered by him into English.
"Thrasa kista aúdug er “Thrasi's chest wealthy is
Under forsi Skoga Under Skogar’s force
Hver sem thángast fyrsti fer Whosoever thither first goes
Fiflskù hefir nóga." Foolishness has enough."
Ref: Symington, Andrew James (1862) Pen and Pencil Sketches of Faröe and Iceland. London.
Ann Humphrey discusses the possible links in Icelandic folklore to Irish influences.
Cerball Mac Dúnlainge, also known as Kjarvalr Írakonungr (Kiarval/Kjarval) (842–888) King of Osraige, has a prominent place in the Icelandic sagas and in the genealogies of the founding families of Iceland as recorded by the Landnámabók. He is described as ruler of Dublin and Earl of Orkney. It has been suggested that the importance of Cerball in Icelandic writings stems from the popularity of the Fragmentary Annals of Ireland among the Norse-Gaels of eleventh century Ireland. The section of the Fragmentary Annals that would have dealt with the death of Tressach are missing. It would interesting to speculate, given the timeframe and the close proximity of the Osraige, the connection between the Barrow River and the Vikings, that Thrasi and his son Geirmund, may have been based on Tressach and Gorman of the Uí Bairrche.
The annal states that Treasach was killed died in 884 AD by Aedh son of Ilguine who may have been of the Uí Bairrche. However, he is not named in the genealogies and the entries in the annal are confused. Ilguine is a very rare name and the only reference found may indicate that it has an Ulaid origin. In the Annals of Ulster (U883 & U886), there are references to Eolóir son of Iergne, who is thought to have been an aggressive leader of the Vikings of Dublin, who may be a more likely candidate.
Ref: Humphrey, Ann C. (2009) They Accuse Us of Being Descended from Slaves. Rutgers University Thesis. http://history.rutgers.edu/honors-papers-2009/152-they-accuse-us-of-being-descended-from-slaves
The following place names in North Scotland, which would have a strong Nordic influence, have been linked to the name Thrasi.
Freswick [earlier name Treswick] — Thrasi's bay (a Scandinavian personal name).
Trossary (South Uist), Trosaraidh. "Thrasi's fertile land", from Norse.
Treshnish in Mull and Tressness in Orkney may mean ' Thrasi's ness.'
There is no proper explanation of the name Trassachs or Trossachs further to the south in Scotland, in what would have been a Gaelic Irish area.
Eyers, Michael (1893) Scottish place names: their meanings explained
Mackenzie, William Cook (1931) Scottish Place-names
Last update: 20 January 2022