The empire of Nilfgaard becomes very important in the Witcher saga starting from the end of Sword of Destiny and continuing through the novels starting with Blood of Elves. The name has always intrigued me (and slightly confused me as I never remember whether it's Nilfgaard or Niflgaard). It looks Scandinavian, with "aa" often being used as an anglicisation of the Scandinavian letter å and gård being a common Scandinavian suffix, but is Nilfgaard in the books written to resemble any Scandinavian culture? The name seems to be preserved by translation, being the same in the original Polish; does it have a Scandinavian ring to the Polish-speaking eye too, or does it mean/suggest something in the Polish language?
What is the origin and significance of the name Nilfgaard?