Pepperoni

Pepperoni is a spicy Italian-American variety of dry salami usually made of pork and beef. Pepperoni is a descendant of the spicy salamis of Southern Italy, such as salsiccia Napoletana piccante, a spicy dry sausage from Naples. Pepperoni is frequently used as a pizza topping in American-style pizzerias. It is the most popular pizza topping in North America.

Pepperoni is a corruption of peperoni, the Italian plural of peperone, referring to the bell pepper, so that ordering “peperoni” pizza in Italy is often an unwelcome surprise for North American tourists, not to mention the surprise of Italian tourists in English-speaking parts of the world who would be expecting bell peppers.

To order the American version of pepperoni in Italy, someone would request salame piccante or salamino piccante (spicy salami, generally typical of Calabria). Throughout continental Europe, peperone is a common word for various types of capsicum including bell peppers and a small, spicy and often pickled pepper known as peperoncino or peperone piccante in Italy and pepperoncini or banana peppers in the US. 

Unlike in Europe, the English word, pepperoni, is used as a singular uncountable noun.