The authors differ on the origin of this surname. R. Brondolo derives it from the Lombard term casari, meaning "cheese producers", and places it as a surname peculiar to Lombardy, with sporadic presence in the Lugano area and in Piedmont.

V. Blunda, on the other hand, proposes for the Sicilian variant a Greek etymology, deriving it from casèas, a term that designated the tanner of hides or furrier. According to this author, the surname would have arisen as a professional nickname applied to those who dedicated themselves to leather work, and is related to the surname Casì, recorded in the same lexical field.

Both proposals suggest an origin in the trade of the bearer, although the etymons and the regions of rooting are different: Lombardy in the case of Brondolo, and Sicily in that of Blunda. The surname therefore presents independent clusters of origin in different regions of Italy.