Serino's history is its water. The springs here fed the aqueduct built under Augustus that carried water the length of Campania — to Naples, around the bay, and to the great cistern at Misenum. It is among the largest works of its kind the Romans built, and its whole purpose was what comes out of this ground. Naples still drinks it.

The name is argued over. Francesco Scandone , the historian of the Irpinian comuni, took it from the Oscan sarino , meaning clear — the spring water set against the muddy Sabato. Filippo Masucci read it instead as sereno , for the clarity of the sky. A third reading takes it from sierra , an enclosure. Above the valley, Monte Terminio is named for Terminus , the god of boundaries, because the mountain marked the edge between two provinces of the empire.

A castle went up in the eleventh century , and in the later twelfth it belonged to the widow of Roberto Sanseverino . But Serino never concentrated into a single town. It is the thirteenth largest comune in the province by area , spread across twenty-four frazioni , and one of its old casali , San Michele di Serino , is a comune in its own right today.

The modern economy is the hazelnut and the chestnut. Since the early 2000s the chestnut gall wasp has done severe damage to the second of those — a sharp break in a very old pattern of work.