Where does “døl” come from?

døl (Norwegian Bokmål) comes from Old Norse dǿll, from Proto-Germanic *dōljaz, from Proto-Germanic dalą, from Proto-Indo-European dʰel- — an arch, vaulting, curve, curvature, cavity;...

døl (Norwegian Bokmål): a person from or living in a valley or valley district, especially one of the major valleys of Eastern Norway