The reference is to "Petrosa", indicating the nature of the mountain landscape, and Podium Odonis, named after Adelaide's husband, to designate the hill of Perosa Alta.

During this period of time (1301–1418), Acaja princes, cadet branch of the House of Savoy, extended their domains to almost all of Piedmont territory using arms and marriages.

The population paid a very high price in term of human lives, owing to wars, epidemics and misery, all consequences of bad international policy choices.

Between XVI and XVII century, the situations in this tormented land was very complex: comings and goings of different armies, alternation of governors, 38 years of French dominance with Francis I and the triumphal entry of Emmanuel Philibert in Pinerolo on the 1st January 1575; the establishment in the valley of Capuchin missions, aimed at curbing the spread of the Reformed religion, took place following the persecutions by Charles Emmanuel I against the Waldensian population.

The same fate had befallen to the Saint John's fort in 1601, built just 4 years before on the rock called "Bec Dauphin", the ancient border between Dauphiné and the House of Savoy (the ruin we can see nowadays was part of a French redoubt).