Just earlier I was reading a wiki about the old province of Musashi, and I was a bit surprised to see a proposal that its name is of Ainu origin and roughly means marsh. I’ve been interested in the name itself for a while, considering how it keeps popping up all over the area of the former province (which includes where I live). On the other hand, I find it quite fascinating that while the English wiki only lists Vovin’s Ainu origin theory for the name, the Japanese wiki doesn’t even mention such a possibility. Remember the axioms of Japanese society:
1) Japan is a homogenous, monocultural society.
2) If reality is otherwise, then 1).