Sorry, I thought you would be Danish speaking when you were referring to Aabenraa and Toender in Denmark. However, I am very interesting in the relationship between BOISEN and BOYSEN and why the change and when. I should be very grateful if you could tell me anything about the origin of the names and why Boisen seem to have changed to Boysen somewhere, somehow.
I am myself Danish, living in London, and my family name is Boysen according to my birth certificate, but my father and grandfather wrote Boisen as if this was the origin of the name. I have cousins with both Boysen and Boisen, quite a confusion within the family. My father's family came from South Denmark, Kolding and Vojens, near the German border like Toender/Aabenraa.