E. De Stefani explains that this surname arose as a Friulian affectionate form of the given name Candido, derived from the Latin Candidus ("pure, candid"). In Friulian, that name takes the form Cjandul, to which a diminutive suffix was added, giving rise to Candolini, which over time became a surname. De Stefani notes that the historical centre of the surname is Interneppo, a locality of the municipality of Bordano, in Friuli, where it is documented at least from the end of the 15th century. Nearby, in Cesclans, there is a small church dedicated to Saint Candidus. The surname is also recorded in Udine and, towards the end of the 19th century, some bearers moved to Tarcento.

E. Rossoni agrees on the dialectal diminutive origin from the name Candido, but develops the phonetic evolution in greater detail: in Friulian, Candido becomes Cjandi, which through the diminutive suffixes in -olo and -ulo gives Cjàndul and then Cjandulìn, a form that was finally Italianised as Candolini. Rossoni also provides the oldest known documentary reference: a mention in the book Cenni storici sul castello di Porcia, of 1629, where a Marco Candolin appears, which would indicate that the transformation into a surname would have occurred at least from the 17th century. Geographically, Rossoni places it in the Udine area —with presence in Gemona del Friuli, Bordano and Fagagna— and also notes a cluster in the Teramo area.