Thule, also called Tile, Ultima Thule, or Toolee, is a symbolic place, the spiritual center, the meeting point between heaven and earth or between the spiritual universe and the material universe.  As is common with spiritual symbols, historian have often tried to make it a physical place with Greenland, Iceland or England being common choices but the original meaning was not about a physical place anymore than the Garden of Eden can be found on Earth (it was never on Earth).  The Nazis believed Thule or Hyperboria was the home of the Aryans.  Thule was a Nordic equivalent of Atlantis, a lost civilization of ancient times where supermen lived, giants with mystical and magical powers (highly developed spiritual people are sometimes called "giants" but it does not necessarily mean they were physically large).
It's not clear if the name Thule started out as a reference to an actual place north of Europe and the name was later used for the spiritual center, or if it was the name of the spiritual center first.  In either case, it appears to me to be a reference to the Sun of Righteousness.