From Wikipedia..

A large number of Italian surnames end in i, due to the medieval Italian habit of identifying families by the name of the ancestors in the plural (which have an -i suffix in Italian). For instance, Filippo from the Ormanno family (gli Ormanni) would be called "signore Filippo degli Ormanni" ("Mr. Filippo of the Ormannos"). In time, the middle possessive portion ("of the") was dropped, but surnames became permanently pluralized and never referred to in the singular, even for a single person. Filippo Ormanno would therefore be known as Filippo Ormanni.[5] Some families, however, opted to retain the possessive portion of their surnames, for instance Lorenzo de' Medici literally means "Lorenzo of the Medici" (de' is a contraction of dei, also meaning "of the"; c.f. The Medicis).

Some common suffixes indicate endearment (which may also become pluralized and receive an -i ending), for example:

• -ello/illo/etto/ino (diminutive "little"), e.g., Bernardino, Bernardello
• -one (augmentative "big"), e.g., Mangione
• -accio/azzo/asso (pejorative[6]), e.g., Boccaccio

• Veneto: -asso, -ato and consonants (l, n, r): Bissacco, Zoccarato, Cavinato, Brombal, Francescon, Meneghin, Perin, Peron, Vazzoler
• Sicily: -aro, -isi and "osso": Cavallaro, Puglisi, Rosso (Sicily and Veneto)
• Lombardy: -ago/ghi and -ate/ati: Salmoiraghi, Bonati
• Friuli: -otti/utti and -t: Bortolotti, Pascutti, Codutti, Rigonat
• Tuscany: -ai and -aci/ecci/ucci: Bollai, Balducci
• Sardinia: -u, -as and -is: Pusceddu, Schirru, Marras, Argiolas, Floris, Melis, Abis
• Piedmont: -ero, -audi, -asco,-zzi: Ferrero, Rambaudi, Comaco, Bonazzi
• Calabria: -ace: Storace
• Campania: -iello: Borriello