The authors differ on the origin and distribution of the surname. E. Rossoni notes that it would derive from a nickname applied to people with a flat nose, although in some cases it could be related to the French surname Camus. Rossoni places the related forms mainly in Lombardy —Milan, Pavia and Alessandria areas for the variant Camussi— and in Piedmont —Turin area, with presence in localities such as Pinerolo, Cumiana, San Secondo di Pinerolo, San Pietro Val Lemina and Perosa Argentina, for the variant Camusso—.

V. Blunda proposes a different etymology circumscribed to Sicily: the surname would come from the Sicilian dialectal expression parlari camusu, meaning "to speak with a nasal voice". In that context, it would have arisen as a nickname applied to people with a nasal pronunciation, a frequent motivation in the onomastics of the island, which records similar designations linked to speech defects.

Both proposals point to a common base related to physical or vocal characteristics, although they differ in the trait alluded to —the shape of the nose according to Rossoni, the nasal voice according to Blunda— and in the regions of origin. The surname therefore presents independent origins in different regions of Italy.