Vietnamese people with the same last name. The existence of last names in Vietnam dates to 111 BC, the beginning of a lengthy thousand-year occupation of the country by the Han Dynasty in China. Before this time, nobody really knows how the Vietnamese handled names, due to lack of written records. In fact even the name “Vietnam” comes from the Chinese; “viet” is the Vietnamese version of the word the Chinese used to describe the people southeast of Yunnan Province.
It is likely that the Vietnamese, prior to Chinese domination, did not use last names, (or family names, which we should call them, given that in Vietnam and many other places, this name does not come last). This does not make them unusual at all. Prior to the 18th century, much of the world did not use family names. More common would be what’s called a “patronymic” name, meaning your full name would literally translate as something like “Steve son of Bob.” Patronymic names refer only to the generation immediately before and remain common in much of the world, especially in Scandinavia and the Middle East.
The entire idea of a family name was unknown to most of the world unless you were conquered by a place that used them. Those conquerors included the Romans, the Normans, the Chinese, and later the Spanish, the Portuguese, the Germans, and the Americans. It was the Chinese who gave Vietnam family names.
So the Chinese just started handing out last names to people. They assigned these surnames pretty much randomly, but the original pool of last names largely came from Chinese last names, or Vietnamese derivations of them. Nguyen, for example, came from the Chinese Ruan.
In Vietnam, the most popular last name is Nguyen. The estimate for how many people answer to it? Somewhere between 30 and 40 percent of the country’s population.
Ruan itself might come from an ancient Chinese state of the same name, or maybe from the ancient lute-like instrument also called a ruan. Who knows? Either way, it seems likely that some mid-level Chinese bureaucrat, in seeking to figure out who actually lived in his newly conquered Vietnamese territory, simply decided that everyone living there would also be named Ruan—which became Nguyen.
The last name, in Vietnam, is there, but just isn’t that important. And when it’s not that important, you might as well change it if a new last name might help you in some way. This may or may not be a continuation of the way names were used before the Chinese came — we really don’t know — but ever since, Vietnamese people have tended to take on the last name of whoever was in power at the time. It was seen as a way to show loyalty, a notion which required the relatively frequent changing of names with the succession of rulers. After all, you wouldn’t want to be sporting the last name of the previous emperor.