It was originally a brand of its own, and predated WWI. Dovo bought the trademark in the 50s, so presumably it was named after the Otto Von Bismarck.

That sounds right, and I found a source for the founding date: 1892, two years after Bismarck retired as chancellor

The family name of the maker was Müller, not Bismarck, and at that point in time, everyone would have thought of the chancellor when reading the name.

Regardless, I need to buy myself one just to have in the rotation

I know that predicament 😅