The authors agree that this surname derives from the Hebrew biblical name ādhām, meaning "man", and that Adam is the first creature according to Hebrew and Christian tradition. F. Miranda specifies that the surname arose from the surname-formation of a founding ancestor's personal name —either because he was so called or because he was born on the day of Sant'Adamo, an abbot celebrated on 3 June—, and that over time it produced variants such as Addamo, Adam, Adamuccio, Adamocci, Adamic and Adamich; the last two, found in the far northeast of Italy, are possibly of Slovenian or Croatian origin.

A. Bongioanni notes that the name was used more among Jews and Protestants than among Catholics, despite being the name of two saints, and that the surnames Molli and Molo could be derivatives of uncertain origin, with documented presence in the Trentino area. For his part, V. Blunda stresses that in Sicily the spread of the surname is linked to the strong rooting of Greek-rite Christianity during Byzantine rule (6th to 9th centuries), when Old Testament names were incorporated into the island's onomastic stock through the biblical lexicon in the Greek language.

Miranda notes that the surname has specific areas of greater concentration in Sicily, Campania, Lombardy, Calabria, Puglia, Lazio, Piedmont and Tuscany, with a presence in various Sicilian provinces such as Trapani, Ragusa, Catania, Messina, Palermo and Agrigento.