In the culinary world, ‘calzone’ refers to an Italian oven-baked folded pizza, much like a turnover made with leavened dough. The dish originated in Naples in the 18th century. The baked, folded pizza-like pocket is usually made of salted bread dough, filled with meats, vegetables, and a variety of cheeses, and would have served as a less-messy way for a workman to carry lunch.

The calzone is similar to a stromboli, an Italian-American pizza turnover, and the two are sometimes confused. Unlike strombolis, which are generally rolled or folded into a cylindrical or rectangular shape, calzones are always folded into a crescent, or half-moon shape, and typically do not contain tomato sauce.

In linguistics, however, calzone’ is the singular form of the Italian word ‘calzoni’ and literally means pants, or trousers. According to the Online Entymology Dictionary, the name is believed to have been chosen because the traditional half-moon shape resembled a trouser leg.

More Info: en.m.wikipedia.org