The name “Eiré” became the chief appellation of Ireland. From “Eire” have been derived the names Eri, Eiriu, Eirin, and lastly Erin: hence, the inhabitants of Ireland have been denominated, in Irish, Eirionach and Eirionaigh, Latinized “Erigena,” “Erigenæ,” and “Erinenses.” As shown by O’Conor, Keating, and O’Flaherty, “Eria,” which is only another form of “Eire,” or “Erin,” was also an ancient name applied to Egypt, and likewise to the island of Crete in Greece, now called Candia. The origin of the names “Eirin” and “Ierne” has been variously explained by antiquaries. Rochart and Villaneuva considered that Ierne was derived from the Phenician words “Iberin” or “Iberne,” which signified the most remote bounds or habitations, as Ireland was then the most remote part of the known world; and Rochart was of opinion, that, as the Greeks did not visit Ireland in those early ages, they got the name “Ierne” from the Phenicians—the only people who had intercourse with Ireland in those remote times, and are therefore considered to have given Ireland the name “Ierne,” which appears to be derived from the Irish “Eire” or “Eirin.” According to Dr. O’Conor, Camden, and others, the name “Eirin” signifies the Western Isle: derived from the Irish “Iar,” the west, and “in,” an island, as being the most western isle of Europe.

Vallancey supposed “Erin” to be the same as “Iran,” the ancient name of Persia; and O’Brien, in his book on the “Round Towers,” maintains the same opinion: namely, that “Erin” or “Irin” is the same as “Iran” or Persia, and says that, in the Persian language, it signifies the sacred land, and that it got this name from the colony of Tua-De-Danans who came to Ireland from Iran or Persia; and it may be observed that the old Irish historians state that Ireland got the name “Eire” from one of the Danan queens. Charles O’Conor, in his “Dissertations,” considers that “Eire” or “Eri” was derived from Erithnea, the name of the country of the Erithneans, who were Phenicians, and a colony of whom came to Ireland. Others derive “Ierne” from the Greek “Ieros,” sacred, and “nesos,” an island, thus signifying the sacred isle, the same as the Insula Sacra of the Roman writers. According to old Irish annalists, Egypt was anciently called “Eria,” which is only another form of the word “Eire’’ or “Erin.”