The authors agree that the surname derives from a nickname or name formed from the medieval Latin word infans (infantis), which means "one who does not yet speak" —from the privative particle in- and the present participle of fari, "to speak"— and which in practice designated a small child. E. De Felice adds that in some cases the origin may lie in the combination of a prosthetic, intensifying in- with the term fante (in Sicilian fanti), a popular variant of infante with the sense of "child" or "boy". E. Rossoni adds that in certain cases it is a surname given to an abandoned child.

As for geographical distribution, Rossoni offers the most detailed picture: the form Infante is proper to southern Italy, especially to Campania, Apulia and the Cosenza area; Infanti is clearly Friulian; Infantini, very rare, shows isolated pockets in Camerota, in the Salerno area, and in Lecce; and Infantino is typically Sicilian and of the Reggio Calabria area, with a presence also in Basilicata and Campania. De Felice, for his part, places the form Infante in central and southern Italy and in Naples, and Infantino in Palermo.