The surname presents multiple independent stocks of origin (ceppi), arisen in different regions without direct relation to each other. E. Rossoni notes that the Lombard cluster could derive from the place name Barni, in the Como area. Alternatively, all the variants could go back to the Lombard name Barna or Barno, to the Celtic name Barna, or to an abbreviated form of the medieval name Barnaba.

V. Blunda, for his part, proposes for the Sicilian stock a different origin: the Greek etymon Barà, a personal name preserved in the Byzantine transmission of southern Italy. According to Blunda, the Italianised spelling would have incorporated the intercalated n when it became a surname along the family line.

The documented forms are diverse. Rossoni records Barna with presence in the Milan area, the Perugia area and Sicily (Agrigento, Palermo and Messina areas); Barnà in the Messina area; Barni in the Milan and Como areas, as well as in those of Pisa, Pistoia and Rome; and Barno, of very scarce presence, in the Varese area and in Sicily.