The reason is that when Vietnam was still in the feudal period, a king ordered the people with the surname of the old dynasty to be changed to the surname Nguyen after the change of power. Over time, the number of people with the surname Nguyen became more and more.

Part of Vietnam was once Chinese territory, but later gradually separated from China amidst the changes of the times.

However, after breaking away from China, Vietnam was still a dependent country of China, so the country's culture was also heavily influenced by Chinese culture. Many surnames in Vietnam were spread from China.

The surname that accounts for the largest proportion of Vietnamese surnames is "Nguyen", and the number of this surname far exceeds other surnames.

The reason why the Vietnamese Nguyen family is so provocative is due to the decisions of the ancient Vietnamese kings.

When Vietnam was still in the feudal period, a man named Chen Shoudu transferred the throne of Li Zhaohuang, the last king of the Li Dynasty, to Chen Yuan. Since then, the Li Dynasty was replaced by the Chen Dynasty.

After the establishment of the Chen Dynasty, the new monarch Chen Xuan was worried that the old people with the surname Li would be dissatisfied with the rule of the Chen Dynasty because they missed the Li Dynasty, so he ordered all people with the surname Li to change their surname to Ruan.

Afterwards, the Chen Dynasty gradually declined, which provided an opportunity for the increasingly powerful Hu family.

Hu Jiyou, a relative, rebelled. After he successfully usurped the throne, the Chen Dynasty was replaced by the Hu Dynasty (also known as Dayu Kingdom).

However, the Chen Dynasty was not willing to perish, so the Chen Dynasty's surviving ministers applied for help from the Ming Dynasty of China. With the help of the Ming Dynasty, the Hu Dynasty only lasted for about seven years and came to an end.

The Chen family, who successfully regained power, ordered all people with the surname Hu to change their surname to Ruan.

Because of this move of the Chen Dynasty, the population of the Nguyen surname in Vietnam gradually increased, and finally became the common surname in this country.

The rising Nguyen surname later successfully overthrew the rule of the Later Le Dynasty and established the Nguyen Dynasty.

After Nguyen came to power, he continued to regard China as his suzerainty.

During this period, the Nguyen Dynasty also expressed to the Qing Dynasty that it wanted to change its name to "Nan Yue", but the Qing court did not agree and gave it another name of "Vietnam".