The world "Real" in portuguese means both royal, real (truth) and the currencry, and "reais" is the plural for all three.

The currency name derives from "royal" and it's a very old name back from the Monarchy days. _However_, during the Monarchy the plural for the old real-the-currency was "réis". Nowadays the plural for the modern real-the-currency (in use since 1994) is reais, like the other standard uses of "real" of the language.