Hmmm, that got me thinking as well... fortunately we have wikipedia, which states the following...

Coffee was introduced into Vietnam in 1857 by a French Catholic priest in the form of a single Coffea arabica tree.[2] The beverage was adopted with regional variations. Because of limitations on the availability of fresh milk, as the dairy farming industry was still in its infancy,[3] the French and Vietnamese began to use sweetened condensed milk with a dark roast coffee.

Source;https://en.m.wikipedia.org/wiki/Vietnamese_iced_coffee

I have learnt so many facts since joining this Blog 😄