The authors agree that this surname derives from the term cappello ("hat"), and refers to trades of maker or seller of hats, although it could also have originated as a nickname linked to physical characteristics of the first bearers.

F. De Laurentiis notes that the surname is widely spread and documents its use in Florence as early as 1260, under the forms Cappellus and Arnaldus cappellaius. F. Miranda adds that the surname could also be related to the place name Cappello, in the Cuneo area, and observes that, in southern Italy, surnames of this type were usually attributed to cultured or aristocratic people, to distinguish them from the common folk.

Miranda also mentions close variants such as Cappelli, Capelli, Capellari and Capelletti, among others, which share the same etymon and original motivation. The surname presents multiple independent clusters of origin, arisen in different regions without direct relation to each other, with presence documented in Sicily, Puglia, Calabria, Campania, Veneto, Lombardy, Piedmont, Lazio, Trentino-Alto Adige and Liguria.