The authors agree that the surname derives from the Latin ferrum ("iron"), although with different nuances. F. Miranda notes that it could have originated in the medieval name Ferro, given to children for whom the temper and resistance of iron was augured, or in nicknames linked to the work of extraction and fusion of that metal. The author of the Alessandria source interprets it directly as a trade nickname related to the working of iron, and documents the form Petrus de Ferro as a member of the Council of Alessandria in the year 1199.

The surname has independent origins in different regions of Italy. Miranda describes it as pan-Italian, present in Veneto and Sicily in a prominent way, but also in Piedmont, Lombardy, Liguria, Campania and Lazio, among other regions. In Sicily, zones of concentration are recorded in the provinces of Messina —with localities such as Caronia and Taormina—, Catania —with Mirabella Imbaccari and Scordia—, Palermo —with Partinico—, Ragusa, Trapani and Enna —with Piazza Armerina and Regalbuto—.