A. Bongioanni notes that Carlo derives from the Germanic given name Karl, meaning simply "man" (equivalent to the modern German Kerl), and that it is one of the most widespread Germanic names throughout Europe. From the French Charles were formed surnames such as the Piedmontese Carle, Chiarle, Chiarletti and Chiarlone, and the Venetian Zarlino. Carlo also enters into composition with names such as Carlantonio or Giancarlo. In Italy, the figure of greatest devotion linked to this name is Saint Charles Borromeo, whose feast is celebrated on 4 November.

V. Blunda, for his part, places it as a surname peculiar to Sicily and specifies that the Germanic root karl designated the "free man" or "adult male in full right". He adds a relevant historical fact: Charles I of Anjou (1226–1285), count of Provence and brother of Louis IX of France, conquered the Kingdom of Sicily after defeating Manfred of Swabia at the battle of Benevento (1266) and established the Angevin dynasty in southern Italy, until the uprising known as the Sicilian Vespers (1282) separated the island from the continental domain.