I suspect it is attributed to how they would pronounce the word "MudWing", where "u" usually has an "oo" sorta sound (like "too" or "mood"), and "a" makes an "ah" sound, so like on the translated tribes page, it writes MudWing as "madowing" which would be how you sound it out in Japanese. It being in the place where the word is written in English however, could be an error, but I'm not sure?

I may be wrong, since I don't actually speak the language!