The name of Sonnino comes from the ancient word SOMMUM that means SUMMIT, and indeed the town was built on the summit of a mountain.
The first document telling about the existence of Sonnino is a Papal Bull of 999.
Accordinf to some historians the origin of this town dates back to the end of 8th century, when the Saracens invaded Priverno and destroyed a large part of southern Lazio, that is to say the provinces of Marittima and Campagna. So the inhabitants of Priverno look shelker there.
Other historians say that Sonnino has a pre-Roman origin; in fact the area was invaded by the VOLSCI.
VOLOSCA (VOLSCA) Street whit ancient ruins (maybe a Roman house) in the district "Sassa", and also a new discovery of a Roman epigraph testify the presence of the Volsci.
But historically talking, Sonnino dates back to the Middle Ages.
At the beginning Sonnino was not a real town but just a remote and unapproachable place, where people and animals wanted to difend from the assaults. So the "shelker" became a sure safety for many people, also from the strange incursions and from the unhealthy climate of the marsh.
A medieval testimony is the imponing Castle with its large cylindrical tower on Sant' Angelo's hill, built in the 9th century by the De Sompenino family who become the first masters of Sonnino. Then the Castle was inhabited by Caetani D'Aragona in 1496 and later by the Colonna family.
Other masters who lived in the Castle for short periods were the Borgia and the Corafo families.
The last owners have been the Antonelli family and the Talani who closed the Castle.