E. De Stefani notes that this surname derives from the old given name Candidotto, a form with the Friulian diminutive suffix -ot (later Italianised into -otto) of the Latin Candidus, meaning "pure, candid". That name had wide diffusion in the province of Udine, with greater density to the north of the city and in the Carnia —the mountainous area of northern Friuli—, and is documented from the mid-13th century in Gemona and Tricesimo. The abbreviated form Candotto appears in the first half of the 14th century. Until the 15th century it functioned as a given name; from the 16th century it became a surname.

According to De Stefani, the centre of diffusion is located in Preone and Enemonzo, in the Carnia, from where the surname spread towards other localities of Friuli-Venezia Giulia, the Veneto and Trentino-Alto Adige, and also towards southern Italy. Clusters are also recorded in areas of southern Austria, such as Klagenfurt and Villach, and in Slovenia, with variants such as Kanduč and Kanduti.

E. Rossoni agrees on the origin from the name Candido, although he describes it as a dialectal modification with an augmentative in -ot, and places the surname mainly in the Udine area, with specific mention of Tolmezzo for the form Candotti and Gonars for the variant Candotto.