E. Rossoni notes that this surname derives from the numerous place names that contain the word Cadore or from the corresponding gentilic, with documented presence in the upper Belluno area and in Bassano del Grappa, in the Vicenza area.

E. De Stefani specifies that it is a surname of ethnonymic origin peculiar to the Belluno area, historically attributed to people coming from the Cadore, the northern zone of the Bellunese. It is documented from the beginning of the 17th century in the Carnia, a mountainous region of northern Friuli, where it appears sporadically in Forni Avoltri and in some minor localities of Enemonzo.

On the derived forms, De Stefani describes Cadorin —with the Friulian ethnonymic suffix -in— as a variant attested in Friulian communities bordering the Veneto, such as Sacile and Caneva, in the Pordenone area, as well as in Trieste and Udine. Rossoni, for his part, places Cadorin in the Belluno and Treviso areas, and mentions the forms Cadori and Cadorini as very rare variants present in the Brescia area. De Stefani adds that Cadorini constitutes a sibling surname of pan-Italian distribution and common etymon.