E. De Felice, E. Rossoni and F. De Laurentiis agree that the surname was formed from the names Severo and Severino, which continue the Latin cognomen Severus —from the adjective severus ("severe, austere")— and its derivative Severinus.

De Felice specifies that both names spread in the Middle Ages through the prestige and the cult of Saint Severus of Ravenna and of Saint Severinus, apostle of Noricum, buried in Naples. He adds that in some cases the surnames may reflect the place names San Severo (in the province of Foggia) and San Severino.

Rossoni recalls among the most celebrated bearers of the name the Roman emperor Septimius Severus (193–211 AD) and the Latin writer and philosopher Severinus Boethius (480–524). Rossoni further distinguishes the forms: Severi is specific to the area that goes from the Parma area to that of Forlì, connecting with that of Arezzo; Severini is more properly of the region of the Marche; Severino is specific to the Naples area, with a presence throughout southern Italy; Severo is infrequent and could be of the Rome area; Severone is almost unique; Severoni is typical of Cittaducale, in the Rieti area, and of Rome.

De Laurentiis notes that the surname is diffused throughout Italy with different frequency, greater in Emilia-Romagna. He agrees on the toponymic base in some cases, from San Severo and San Severino.