James Adair has been called by various writers an Englishman, a Scotchman and an Irishman—and with some basis of fact in each case. He derived from the historic Irish house of Fitzgerald. Indeed, Fitzgerald was his true name. That family descends from Walter, son of Other, who at the time of the Domesday Survey (1086) was castellan of Windsor and tenant-in-chief of five of the counties of England. His descendants took active parts in the conquest of Ireland, where one of them in 1346 came into the Earldom of Kildare. Another line of the Fitzgeralds was that of the Earls of Desmond, which also descended from Maurice, the founder of the family in Ireland. The Desmond branch, under the third earl, who was viceroy of Ireland in 1367-69, became embroiled in difficulties and suffered defeat, and was captured by a native king of Thomond.
