The Diavola pizza is better known as Pepperoni pizza out of Italy. Diavolo means “devil” and it is meant to refer to the fact that it should be “hot as hell”. This has something to do with the hot peppers contained in the spicy sausage used to finish it… We called them peperoncini.
Pepperoni does not exist at all as an Italian word, it is an entirely American thing. If you ever happen to travel to Italy, and order a Pepperoni, you will end up with a pizza full of bell peppers.