The fallacies which I have to expose were unknown to the Irish people until towards the close of the last century; the writers of an earlier period having been too well informed to lead their readers into error. But their works being for the most part in a dead language, and very rarely to be met with, they ceased to have an influence on the public mind, and left the way open for a new race of writers, very ignorant of the ancient language and history of Ireland, to impose their crude theories upon the uninstructed reader. A society of such persons, of whom General Vallancey, Mr Beauford,[2] and Dr Ledwich, were the most active, was formed for the purpose of giving to the public a series of essays on the antiquities, ancient literature, and topography of Ireland; and the result of their joint labours made its appearance in a work published periodically under the title of “_Collectanea de Rebus Hibernicis_,” and since popularly called Vallancey’s Collectanea. These gentlemen, however, after a time found that their systems had nothing in common, each considering the other as insufficiently informed on the subjects treated of, and I think, with justice; for, as I trust I shall be able to show on a future occasion, all were alike ignorant of the matters they professed perfectly to understand. But though the labours of these gentlemen contributed generally to the propagation of erroneous theories on the subject, it was a work of Mr Beauford’s, published in No. II of the Collectanea, which, treating more immediately of this subject, has had the greatest influence on the popular mind; an influence less owing to any celebrity attached to his own name than to that of Vallancey, whose sanction and approbation this work is generally supposed to have received. With this writer originated the novel theory that the names of tribes and families in Ireland, as usual among the Saxons and Normans, were derived from earlier appellations of the territories and localities which they occupied. To establish this hypothesis he adopts a process of etymological investigation unparalleled in the annals of antiquarian research. In the first place, he takes the liberty of dividing the words into as many parts as he thinks proper; secondly, he makes such changes in the vocables thus obtained as he finds convenient to his purpose; thirdly, he gives each of these words new meanings of his own; and lastly, he places the tribes whose names he thus explains in localities which many of them never occupied.