The authors agree that the surname derives from a personal given name: E. Rossoni links it with the Norman name Rouger or with the Germanic Roger, a contraction of Rodigerius, and recalls as historical figures the Marquis of Monferrato at the beginning of the 13th century and the Marquis Ruggi d'Aragona, documented in Salerno in the 18th century. S. Vannozzi specifies that in Cercemaggiore, in the Campobasso area (Molise), the surname is documented from the 16th century, with the first known ancestor recorded as Ruccio De Ruccio, and that the old variants Ruccio, Ruggio and Rugio arose from the transformation into a surname of that basic given name.

The surname presents multiple independent lines of origin (ceppi), arisen in different regions without a direct relation between them. According to Rossoni, the form Ruggi is located in the Modena, Campobasso and Taranto areas; Ruggia appears in Rome, in the Salerno area (Eboli, Campagna), in the Reggio Calabria area (Locri) and in the Agrigento area (Menfi); Ruggio is concentrated in Rome and in the Lecce area; and the variant Rugi is recorded in Tuscany, in the Florence and Siena areas.