Right. Just like in Viet Nam, most common family name is "Nguyen." It's the "Smith" of that country and has ties to their ancient, long disappeared monarchy. Tran, Pham, and some other "last names" are also common but Nguyen is first on the list. Thus, when all the Vietnamese boat people started arriving in USA with names that in their country were like Nguyen Thi Oanh or Nguyen Cao Trang they were routinely switched around to Oanh Thi Nguyen, Trang Cao Nguyen, etc. Or they became even more Ameicanized as a Suzy Nguyen or a Jimmy Nguyen. I've traveled in East Asia a lot over the years and to this day I'm often referred to in Philippines as "Joe" or in Viet Nam as "Bob" - simple names they often assign as easy to say/remember for any American male visitor. In Asia, the native person is usually addressed with the family name first, so simply saying "Yao" is entirely customary.