Athon de Courtenay, Lord of Courtenay and castellan of Chateau-Renard, fortified Courtenay, in Gatinais in the Isle de France c1010. [Burke's Peerage]
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The Courtenays, of whom a distinguished line still exists, were one of the most illustrious races amongst the British nobility, and deduced their pedigree paternally from Athon, who himself descended from Pharamond, found, in 420, of the French monarchy, and common patriarch of all the Kings of France. This Athon, having fortified, during the reign of Robert the Wise, the town of Courtenay, in the Isle of France, thence adopted his surname. But as the power of the Courtenays in England principally arose from the great alliances formed by the first members of the family who settled here, we shall pass at once to their maternal pedigree. [Sir Bernard Burke, Dormant and Extinct Peerages, Burke's Peerage, London, 1883, p. 139, Courtenay, Barons Courtenay, Earls of Devon]
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Athon de Courtenay, Sire de Courtenay in the G‚tinais and of Ch‚teau Renard; built the castle at Courtenay, 1010. [Roderick W. Stuart, Royalty for Commoners, 3rd ed., Genealogical Publishing Company, Baltimore MD, 1998]