Dutch and Norwegian are also closely related. It would be surprising if there weren't transitivity there—and IIRC there are examples where the relationship doesn't hold in both directions. I remember reading somewhere that Dutch speakers have an easier time understanding German than vice versa, despite both being similar.
There was a lot of trade between the two countries for some time. Norwegians would travel around to Bergen or other coastal towns on the west coast and then would trade with the Dutch and the Germans.
