The authors agree that this surname derives from a nickname of medieval origin linked to the term "deacon". F. Miranda specifies that the word comes from the Greek diàkonos and the Latin diaconus, with the meaning of "servant" or assistant to the priest in religious functions. Miranda adds that the surname, together with its variants (Iacono, Iacomelli, Iaconi, Iaconis, Jacono), alludes to the function the first bearer of the name would have performed.

E. Rossoni notes that the form Lo Iacono is of Sicilian origin, although the variant Loiacono would show two specific areas of presence: one in Calabria and another in the Bari area. Miranda confirms the strong Sicilian concentration of the surname, with a presence in every province of the island, especially in Palermo, Messina, Caltanissetta, Agrigento and Trapani. He also documents it in the Enna area and in various regions of the rest of Italy, such as Lombardy, Piedmont, Lazio, Tuscany, Campania, Emilia-Romagna, Calabria, Liguria, Puglia and Abruzzo, though with a less numerous presence.