E. De Stefani identifies this surname as a Friulian microtoponymic, documented at least from the middle of the 16th century in Sutrio, and also present in Rivo, a frazione of Paluzza, both localities in the Carnia, a mountainous zone of the north of Friuli, in the province of Udine. It derives from the dialectal word (a)ronc, used in the Carnia to designate a mountainous terrain deforested and put under cultivation, a term that goes back to the Latin runcare, "to weed" or "to clear". The surname thus reflects the historical practice of clearing mountain terrains for cultivation.

De Stefani also notes that the spellings Da Ronco, D'Aronco and Daronco are graphic and prepositional variants of the same Friulian surname, present in other zones of the region. He considers surnames related by the same etymon —with their own distribution— to be Ronca, Roncalli, Roncati, Ronchetti, Ronchi and Roncoroni, documented mainly in Lombardy and in the Swiss Ticino.

E. Rossoni, on the other hand, proposes a different toponymic origin: the surname would derive from the name of some locality called Ronco, such as Ronco in Trentino or Ronco all'Adige in the Verona area, indicating the place of provenance of the founding ancestor.