Well, apart from it being named "Dong" it is also the currency with the highest numbers on its bills. Worldwide.
There is a 500,000 Dong bill and it is not an exotic one like the 500 € bill, that you hardly ever came across in everyday life. Half a million Dong will only get you the equivalent of (roughly) 20 € or $. So usually, after coming back from the ATM, you will be a multi millionaire in Vietnam.
That seems cool first, but is really confusing in reality, because locals hardly ever say the complete number when talking prices. "Two hundred thousand" just becomes "two hundred" and might make you search for a bill so small, it does not even exist (you might not see anything smaller than 1,000).
This of course only happens because your sense of value gets thrown off quickly in a country where the best food you ever had might just cost two Euro, but needs you to grab for a bill that says 100,000.
There is one big benefit of the high numbers on Vietnamese bills though: no annoying coins. They just do not exist in everyday life.