i believe that the gesture originates in the south, rome, sicily, naples... it's most widely known due to the immigrants in New York and their big presence in the movie business relating to that, and i believe they are mostly from the southern regions

i'm not ignorant of the differences, i have been in italy for a whole month walking around and saw rome, nettuno, avezzano, popoli, forlimpopoli, rimini, bologna and venice, i know they are all very different, i like the southern people better, and for me bologna was the most unpleasant and fascist shithole in the country... venice seemed extremely industrialised, and very smelly canals