By 1261, the weakening of the Anglo-Norman Lordship had become manifest following a string of military defeats. In the chaotic situation, local Irish lords won back large amounts of land. The invasion by Edward Bruce in 1315-18 at a time of famine weakened the Norman economy. The Black Death arrived in Ireland in 1348. Because most of the English and Norman inhabitants of Ireland lived in towns and villages, the plague hit them far harder than it did the native Irish, who lived in more dispersed rural settlements. After it had passed, Gaelic Irish language and customs came to dominate the country again. The English-controlled area shrank back to the Pale, a fortified area around Dublin. Outside the Pale, the Hiberno-Norman lords intermarried with Gaelic noble families, adopted the Irish language and customs and sided with the Gaelic Irish in political and military conflicts against the Lordship. They became known as the Old English, and in the words of a contemporary English commentator, were "more Irish than the Irish themselves." The authorities in the Pale worried about the Gaelicisation of Norman Ireland, and passed the Statutes of Kilkenny in 1366 banning those of English descent from speaking the Irish language, wearing Irish clothes or inter-marrying with the Irish. The government in Dublin had little real authority. By the end of the 15th century, central English authority in Ireland had all but disappeared. England's attentions were diverted by the Hundred Years' War  and then by the Wars of the Roses . Around the country, local Gaelic and Gaelicised lords expanded their powers at the expense of the English government in Dublin.

What did the Hibero-Norman lords do to become known as the Old English?
intermarried with Gaelic noble families