Sky and Sea

Now there shall be told more of the underlying stories from
which those kennings just listed have originated, and of which the
origins have not already been told, just as Bragi told Ægir how
Thor had gone to eastern parts to thrash trolls, but Odin rode
Sleipnir into Giantland and arrived at a giant’s called Hrungnir.
Then Hrungnir asked what sort of person this was with the golden
helmet riding sky and sea, and said he had a marvellously good
horse. Odin said he would wager his head on it that there would
be no horse as good to be found in Giantland.


- Prose Edda, Skaldskaparmal