Norse Mythos in MS?

You meant Nifelheim (or Niflheim) which was half of the cause of Ymir's creation. Nibelheim is freaking in ff7. Well I blame Squaresoft for such a misleading reference. D:

Yes, Nifelhem would be the correct name, but Nibelheim works too, look at Wagner's Nibelungen. You're right about the Ymer part though, from the frost of Nifelheim and the firey sparks of Muspelheim came the giant Ymer, which Odin and his brothers Vile and Ve later slew. They used the carcass to make the world according to the creation myth of theirs.

Ill give you a few more variations just for the hell of it:

Ymer=Ymir
Mjölner=Mjolnir
Gungner=Gungnir
Oden=Odin
Tor=Thor
Freja=Freya
Ragnarök=Rangnarok
Midgård=Midgard
Asgård=Asgard
Midgårdsormen=Miðgarðsormr=Jormundgand=Jörmungandr

Mostly small variations, but still.