The authors agree that this surname derives from the term designating the ecclesiastical grade of deacon, in its southern form iácono, found in Sicilian and Calabrian as iácunu. The surname would therefore have originated as a nickname or office-name applied to the first bearer of that religious function.

F. Miranda broadens this base by noting that the deacon comes from the Greek diàkonos and the Latin diaconus, meaning "servant", or assistant to the priest in religious functions. Miranda also points to a second hypothesis: that some forms of the surname could derive from variants of the given name Giacomo, of biblical origin, from the Greek Ἰάκωβος (Iakobos), itself from the Hebrew Ya'aqov.

Miranda further documents a wide range of variants, altered forms and derivatives: Iacona, Jacono, La Iacona, La Jacona, Lo Iacono, Lo Jacono, Lojacono, Iacomelli, Iaconi and Iaconis. The greatest concentration of the surname is recorded in Sicily —especially in the Agrigento, Ragusa, Syracuse, Catania and Palermo areas— and in Campania, particularly in the Naples area.