The vast extent of the territory conquered and colonised by the Celts, and the unity of their speech, may be conjectured from an examination of the place-names of Celtic origin which either still exist or figure as having existed in European history.[1] The Celts seem to have been first known to Greek--that is, to European history--under the semi-mythological name of the Hyperboreans,[2] an appellation which remained in force from the sixth to the fourth century before Christ. The name Celt or Kelt[3] first makes its appearance towards the year 500 B.C., in the geography of Hecatæus of Miletum, and is thereafter used successively by Herodotus, Xenophon, Plato, and Aristotle, and from that time forward it seems to have been employed by the Greek scholars and historians as a generic term whereby to designate the Celts of the Continent. Soon afterwards the word Galatian came also into use,[4] and was used as a synonym for Celt. In the first century B.C., however, the discovery was made that the Germans and the Celts, who had been hitherto confounded in the popular estimation, were really two different peoples, a fact which Julius Cæsar was almost the first to point out. Diodorus Siculus, accordingly, struck by this discovery, translates Cæsar's _Gallus_ or Gaul by the word Celt, and his _Germanus_ or German by the word Galatian, while the other Greek historian, Dion Cassius, does the exact opposite, calling the Celts "Galatians," and the Germans "Celts"! The examples thus set, however, were the result of ignorance and were never followed. Plutarch treats the two words as identical, as do Strabo, Pausanias and all other Greek writers. The word Celt itself is probably of very ancient origin, and was, no doubt, in use 800 or 1,000 years before Christ.[5] It cannot, however, be proved that it is a generic Celtic name for the Celtic race, and none of the present Celtic-speaking races have preserved it in their dialects. Jubainville derives it, very doubtfully I should think, from a Celtic root found in the old Irish verb "ar-CHELL-aim" ("I plunder") and the old substantive to-CHELL ("victory"); while he derives Galatian from a Celtic substantive now represented by the Irish _gal_[6] ("bravery"). This latter word "Galatian" is one which the German peoples never adopted, and it appears to have only come into use subsequently to their revolt against their Celtic masters. After the break-up of the Celtic Empire it was employed to designate the eastern portion of the race, while the inhabitants of Gaul were called Celtæ and those of Spain Celtici or Celtiberi, but the Greeks called all indifferently by the common name of Galatians. The Romans termed the Celts Galli, or Gauls, but they used the geographical term Gallia, or Gaul, in a restricted sense, first for the country inhabited by the Celts in North Italy upon their own side of the Alps, and after that for the Celtic territory conquered by Rome upon the other side of the Alps.