Aesernia

The origins of Isernia are as yet certain not defined. A lot of historical information comes from the Samnite wars.  According Livy X. 31,2 ..and the Samnites made predatory incursions on the territories of Vescia and Formiae; and also on the other side, on those of Aesernia, and the parts adjacent to the river Vulturnus. The city's Roman name, Aesernia, reflects probably a former Samnite toponym, The cyclopean walls that were usually built by the Pelasgians sugest earlier date of the origins.

Sources:

1. Livy. History of Rome by Titus Livius, books nine to twenty-six. literally translated, with notes and illustrations, by. D. Spillan. and. Cyrus Edmonds. York Street, Covent Garden, London. Henry G. Bohn. John Child and son, printers. 1849 - Liv. X. 31; XXVII, 10; XL.40
2. Domenico Romanelli, Antica topografia istorica del regno di Napoli, Napoli, 1818, p. 468.