My guess would be East Prussia. This area was inhabited by a people called Old Prussians or Baltic Prussians in English, Prußen or Pruzzen in German, Prūsai in their own (now extinct) language. One of their lands was called Nadrauen (from na-drawa: there where it flows). These people got rapidly assimilated by Lithuanian and German immigrants after the 13th century. In the 15th century a Prußian named Nedrow is documented as the owner of the estate Bledau in East Prussia.
Nedrow, NY is a hamlet in Onondoga, NY, an area that was populated by German immigrants. Given how rare the name appears to be it seems possible that it spread from East Prussia through Prussia and then to the US via German immigrants.