Generalising such rules you either end up getting into tangled mess of argument similar to sibling thread or it'll be too generic to be of any use or worse. So

Generalising such rules you either end up getting into tangled mess of argument similar to sibling thread or it'll be too generic to be of any use or worse. So no, please don't do it by North/South India etc., You go state by state and learn about common upper class surnames. To pick a Maharashtra sized hole in your rule, how would you categorise Chitpavan brahmin's surnames? Godbole, Phadke, Godse etc., don't even trace their origin to Sanskrit.