Polish an russian folklore is very similar, as both are slavian nations (well, not exactly - there are A LOT more devilish entities in polish folklore ). Also the languages are very similar, so the explanation may be true, as Bog really means God, but i still think that the name came from Belarus
Polish slavian nations would be have surely a lot of D magic, also some nice N,E,W.
I still think there must be some hidden beatiful name in the mythology that could fit the nation better I am back home now so I can get into that topic and look at the mod.