Parmigiano is the Italian adjective for Parma. Reggiano is the Italian adjective for Reggio Emilia. In the US the name Parmesan is used for cheeses which imitate Parmigiano-Reggiano, along with phrases such as “Italian hard cheese”.
According to legend, Parmigiano-Reggiano was created in the course of the Middle Ages in Bibbiano, in the province of Reggio Emilia. Its production soon spread to the Parma and Modena areas. Historical documents show that in the 13th and 14th centuries, Parmigiano was already very similar to that produced today, which suggests its origins can be traced to far earlier.
It was praised as early as 1348 in the writings of Boccaccio; in the Decameron, he invents ‘a mountain, all of grated Parmesan cheese’, on which ‘dwell folk that do nought else but make macaroni and ravioli, and boil them in capon’s broth, and then throw them down to be scrambled for; and hard by flows a rivulet of Vernaccia, the best that ever was drunk, and never a drop of water therein.