The origin of the name of Castropignano is very uncertain: several scholars believe it derives from one of the settlements of the Samnites Pentri, Castrum Expugnatum, practically razed to the ground during the wars with the Romans. 
Others instead derive the name from "Palombino del Sannio Pentro", also destroyed by the Romans in the year 419 BC. 
The first settlements in the territory of Costropignano can be traced back to the V-IV century. AC. by Samnite shepherds.