Though this is recognizably what we call Celtic knotwork, the subject is of course Norse.

If I were going to defend that I'd point out that prior to the seventh century, you were more likely to find patterns like knotwork on Saxon or Scandinavian artifacts than on Scottish or Irish; I might add that though these groups were culturally distinct there are many examples in their languages that are clearly related (like the Irish "Rig" vs. the Germanic "rik" for king, or the very words "Teuton" vs. "Tuatha" for words meaning tribe.

But I'd never mention that, because it could get me beaten up in so very many bars in so many parts of the world that I'd be a fool to talk about it.

So anyway. Here's Mjolnir, Thor's hammer, composed of intricate knotwork like an ancient piece of jewelry; including two serpents, who remind us of Jormungandr, the Midgard Serpent - whose fate was entwined with Thor's.