This is Nordic. Nordic art and Celtic art have a lot of similarity. I'm most familiar with Celtic but have been getting to know Nordic recently.

Edit: I forgot to add, this tattoo is three intertwined triangles. It is not a knot. Triquetra knots are based on a single line (a knot), sometimes with a circle intertwined.

This is Nordic. Nordic art and Celtic art have a lot of similarity. I'm most familiar with Celtic but have been getting to know Nordic recently.