(Only to clarify that „bögge“ is not a German word to the best of my
knowledge. I was looking, as it sounded so »northern«,
And so it is: it's Low Saxon, and also exists in the compound form "böggel-mann", plainly cognate to British English "bogeyman", American English "boogeyman". Or borrowed one way or the other: there is so much borrowing and convergence in the Germanic languages around the North and Baltic Seas that if we did not know the older varieties of these languages we would never be able to work out just how they are related.