Kepler starts Somnium in Iceland, of which he wrote (in a footnote):
In our German language this means “land of ice.” Of this truly remote island I have perceived I can sleep and dream, in imitation of the philosophers who wrote of these [things]. For Cicero crossed into Africa when he was going to dream; and Plato invented Atlantis in the western ocean, to summon mythical aids to military valor; and finally, Plutarch, in his small book, The Face in the Moon, after much discussion, describes the location of islands over the ocean that modern geographers would probably apply to the Azores, Greenland and the territory of Labrador, regions around [Iceland].
In Kepler’s time, the New World was barely known of in Europe and Iceland was at the end of the Earth. Plutarch seems have thought there was some sort of magical portal to other worlds there, and Iceland was said to be a place of magic and witchcraft, a reputation well-justified:
In another footnote, Kepler explained that he chose the name “Duracotus” because it sounded Scottish:
The sound of this when spoken was suggested to me by recollecting names with similar sounds from the history of Scotland, a region which looks over the ocean [to] Iceland.
… and so maybe he thought that the Scottish and Icelandic cultures were related. But he wrote in a third footnote that he derived the name “Fiolxhilde” from the unknown word “Fiolx” that he once saw written beside Iceland on an old map; Kepler was “pleased with its grim sound.”
The Somnium Project 