The authors differ notably on the origin of this surname. A. Bongioanni links it to classical Latin: he considers it a given name peculiar to an illustrious Roman gens, whose origin would not derive from the word cornus but possibly from the city of Corne. He notes two saints with this name: Pope Cornelius, a martyr in the year 252, whose feast is celebrated on 16 September, and the centurion Cornelius, converted by Saint Peter and a martyr under Tiberius, celebrated on 2 February. Bongioanni indicates that the name was not much used and that the surname exists in Piedmont.

B. Zuanella, on the other hand, documents a particular case in which the surname has no relation to the Roman name. According to this author, the surname present in Ponteacco —a locality of the Natisone valley, in the region of Friuli-Venezia Giulia— derives from the ethnic Carniel, equivalent to "Carnic", that is, native of the Carnia. It originally designated a weaver moved from that zone towards Staro Selo, near Caporetto. The original surname, Carniel or Carnel, was gradually transformed into the altered form Cornelio, which became consolidated in local use and lasted until contemporary times.