The name Gennaro has an origin clearly linked to the Christian tradition and to the city of Naples. It derives from the Latin Ianuarius, meaning "relating to January" (Ianuarius = the month dedicated to the god Janus), although its diffusion and meaning in Italy are deeply marked by the cult of San Gennaro, bishop and martyr of the 4th century. From this cult, the name acquired a very strong devotional value, associated with divine protection and Neapolitan identity.

As for its diffusion, Gennaro is especially characteristic of southern Italy, and in particular of Naples and the whole region of Campania, where it is one of the most traditional and representative names. Its use also spread to other zones of the Mezzogiorno, though always with much less intensity outside that sphere. This strong regional concentration explains why many variants of the name —such as Zennaro in the north— arise by dialectal adaptation, but keep the original reference.

As a whole, Gennaro is not only a name of ancient origin, but also a clear cultural and territorial marker, deeply tied to the history, the religiosity and the identity of Naples.