The authors agree that this surname derives from a term referring to the trade of maker or harness-maker of saddles. E. Rossoni links it to the medieval Latin word sellarius, with records of its transformation into a surname in Como from the second half of the 14th century. V. Blunda, for his part, places it in the Sicilian sphere and connects it with the dialect word sellàru, "harness-maker of saddles," noting that the suffix -àru is characteristic of the Sicilian trade names formed on the manufactured object.

Rossoni describes the surname as very rare and with independent origins in different regions of Italy. He identifies a line in the Perugia area and another in the area comprised between Rome and Frosinone. He further notes related forms: Sellaro, typical of Calabria, and Selleri, whose main nucleus is found in the Bologna area.