Estados Unidos = EE.UU. Why not E.U.?
This is a common question I get. The answer is very simple.
In Spanish, when we want a word to be “initialized” (for the sake of this explanation we are going to assume that “to initialize” means “to write the initials of a word”), we have to use double letter if the word is in plural. See the examples below:
- Estados Unidos EE. UU.
- Naciones Unidas NN. UU.
- Relaciones Públicas RR. PP.
- Recursos Humanos RR. HH.
- Servicios Higiénicos SS. HH.
That was a short and easy explanation to give.
Taken from Keeping Spanish Simple.