from the Frederick III Ordway Collection, US Space & Rocket Center:

The first two notes prepared by Kepler for his Somnium, which was published posthumously in 1634. In the first note he referred to the name Duracrotus (the book’s hero) and to the fact that “The sound of this word came to me from a recollection of names of a similar sound in the history of Scotland, a land that looks out over the Icelandic Ocean.” In the sec¬ond note he begins by explaining that Iceland, Duracrotus’s home, “means ‘land of ice1 in our German language. I saw in this truly remote island a place where I might sleep and dream and thus imitate the philosophers in this kind of writing. . . .”  

Duracrotus is usually given as Duracotus (with no second ‘r’) by most translators of Somnium to English.

The notes on this page by Kepler also notes the legend related by Plutarch (46 – 120 AD) in a discussion of the moon and other matters, that distant and mysterious Iceland was said to be a gateway to other worlds.