While a lot of us believe that Guanciale is from Rome, we are wrong. It definitely comes from Abruzzo, specifically from a place called Amatrice, near L'Aquila.
Despites our profuse research, we haven't been able to trace the origins of this important cured meat. What we know is that it is broadly used throughout Italy in a variety of recipes that make it the King of the Italian cuisine.
As previously mentioned under the Pancetta section, Guanciale is not to be confused as they are different meats. Nevertheless, in Australia, it's not always easy to find Guanciale and it can be replaced with Pancetta in some recipes.