Kneen talking about the 1422 revolt (in personal names - see manxnotebook) has
"Among the rebels was a Manxman whose forebears evidently hailed from Ireland, for his name was Donald Waterford. His ancestor evidently came from that city, and in the first instance 'Waterford' or 'of Waterford' would be a kind of nickname bestowed on him by the Manxmen. But the name apparently disappears, and no doubt Waterford was executed and his farm confiscated. After this there is no record of the family for well over a century, but he must have left either relatives or descendants, for at the opening of the 17th century we find that one of them had managed to acquire an upland farm in Kirk Christ Rushen, and his name and rental are duly entered in the Manorial Roll of 1601. In the intervening years a metamorphosis of the name had taken place-Waterford had become Watlefoorth-and the name still flourishes around Port Erin and Port S. Mary in the further corrupt form, Woodworth"

Looking at directories etc there is a great concentration around Port Erin with major family that of Thomas Woodworth + Isabel Crebbin