This Irish surname was first anglicized O'Hagherin, which is a fair phonetic approximation of the original Gaelic O'hEachtighearna, derived from the Irish words each a horse and tighearna a lord. Later this was corrupted to O'Ahearne and finally the prefix O was dropped. The O'Ahernes were originally a Dalcassian sept and up to the middle of the fourteenth century they were dynasts of Ui Cearnaigh, their territory being in the neighbourhood of Sixmilebridge, Co., Clare, not far from the city of Limerick. In the course of time they migrated southwards and in 1659, when Petty's census was taken, the name was numerous throughout Counties Cork and Waterford. At the present time it is almost confined to Counties Cork and Limerick; but in the form Hearn and Hearne it is also well established in Co. Waterford. In this connexion it should be observed that Hearn is a fairly common indigenous name in England, so that persons so called in Ireland may be immigrants from that country. The Bishop of Kerry from 1336 to 1347 is described in the records as Alan O'Hathern alias O Hachierane. The most noteworthy of the name in modern history were John Aherne (c. 1769-1806), United Irishman and intimate friend of Wolfe Tone, who after the latter's death became an officer in Napoleon's Irish Legion; and John Aheron author of the first book on architecture printed in Ireland (1754). The Gaelic name O hUidhrin, that of an Offaly sept, has also been anglicized Hearne, Heron etc., though Heffron and Haveran are more usual forms in English. Giollananaomh OhUidhrin (d. 1420), who completed O'Dugan's celebrated "Topographical Poem", is usually O'Heerin in English.