According to Wikipedia, after he and his fellows explored a bit, they returned to their men to tell them about the land, and his report was "all the straw is covered in butter". I don't understand what was meant by that. Was it supposed to be good? Bad? Thanks, historians!
http://en.wikipedia.org/wiki/Hrafna-Fl%C3%B3ki_Vilger%C3%B0arson
I noticed this article doesn't have any sources cited, so maybe it's not true? Either way, thanks.
I cannot comment on why but I can come up with a small fun fact.
Here in Iceland we still have a saying: hér dýpur smjör af hverju strái. Which literally means here the butter drips from every blade of grass.
It doesn't. But that is a topic for a whole new discussion.
It's an idiom meaning there are many opportunities. The earth is fertile, that kind of thing. Cows eat straw/grass and out of cow milk they make butter.