'Nguyen' is a popular Vietnamese family name (surname). It is, in fact, the most common Vietnamese family name. By some estimates, roughly 40% of Vietnamese people have the last name Nguyen.
The name Nguyen is considered to be of Chinese origin, from the Chinese instrument Ruan, which is a plucked string instrument.
The prominence of this family name in Vietnam is largely predicated upon the success of The Trần dynasty, overthrowing The Lý dynasty after 1232. The Trần dynasty subsequently coerced all the descendants of the Lý into changing their names to Nguyen.
When The Nguyễn Dynasty (Nguyen Lord descendants) eventually won power in 1802, several descendants of other Lords also changed their names to Nguyễn, fearing punishment and retribution.
This dynasty bestowed the Nguyễn name onto many people during their rule, it is also known that many criminals reverted to the Nguyen name to avoid prosecution, since they were aligning to the rule at the time.
I hope this helps you to understand the origin behind the name 'Nguyen', and why it is such a prominent family name.
