I think you did not get Wodnenus's point. During that time people do dont travel so much since transportation technology is not that advance like today. As such people are ignorant about strange races for distance land. China has so many dialects that it is not so easy for people to tell their location base on their dialect. Even today (with our information age), some still have may not be able to tell easily.
Now you are confusing me. I thought singh is a surname for those whose religion is sikhs. I am surprise that it is a surname for all punjubis.

singh is not a surname. Its a sort of a prefix thing for all the sikh guys. Sikh girls always have the word kaur behind their names.
Surnames are, for example, Gill, Rekhraj, Sidhu

like mine is rekhraj. My full name is anildip singh rekhraj ------> rekhraj being my surname from my ancestors
i have a friend who is anildip singh gill.... so thats his surname...