E. Rossoni notes that Cogoi is peculiar to the lower territory of Udine, with presence in localities such as Muzzana del Turgnano, Lestizza, Mortegliano and Manzano, and also in Trieste. He also records the variants Kogoj, peculiar to the Gorizia area and to Savogna d'Isonzo, and Kogoi, present in the Udine area. According to Rossoni, these forms could derive from the Friulian word cogói, which designates a type of hemp net for catching freshwater fish.

B. Zuanella broadens this etymology by noting that the Friulian noun Cogòl or Cogòi refers specifically to a buitrón, a cone-shaped net used to catch chub, barbel and eels, and that the surname would have arisen by metonymy to designate a freshwater fisherman. Zuanella also gathers the hypothesis of Pavle Merkù, who considers the Friulian origin of the surname probable given its diffusion. Nevertheless, he notes that the ending -goj could respond to an ending of Slavic origin, present in numerous Slovene surnames such as Saligoi, Bodigoi or Cernogoi, a hypothesis that he considers likewise valid.

Zuanella also documents that the surname was present in the 17th and 18th centuries in the valleys of San Leonardo —in localities such as Lusa/Luža, Gnidovizza, Stregna and Osgnetto—, where it is today extinct, and that it is currently spread in Slovenia.