Many years ago, I had a girlfriend who had a German friend living in Hamburg, which as you all know, is on the Baltic coast of Germany. Whenever she came over to visit, if she came along to a session she always asked me to sing the 'Wild Rover' as it had the same tune as a German folk song she had learnt as a child - which makes sense when you think of it. You can certainly imagine a German oompah accompaniment if you're that way inclined. And I suppose it's not impossible that the tune may have found it's way to East Anglia from Germany. Or vice versa.