The earliest Celtic "kingdom" was in the region between the upper waters of the Rhine, the Elbe, and the Danube, where probably in Neolithic times the formation of their Celtic speech as a distinctive language began. Here they first became known to the Greeks, probably as a semi-mythical people, the Hyperboreans--the folk dwelling beyond the Ripoean mountains whence Boreas blew--with whom Hecatæus in the fourth century identifies them. But they were now known as Celts, and their territory as Celtica, while "Galatas" was used as a synonym of "Celtæ," in the third century B.C.[44] The name generally applied by the Romans to the Celts was "Galli" a term finally confined by them to the people of Gaul.[45] Successive bands of Celts went forth from this comparatively restricted territory, until the Celtic "empire" for some centuries before 300 B.C. included the British Isles, parts of the Iberian peninsula, Gaul, North Italy, Belgium, Holland, great part of Germany, and Austria. When the German tribes revolted, Celtic bands appeared in Asia Minor, and remained there as the Galatian Celts. Archæological discoveries with a Celtic _facies_ have been made in most of these lands but even more striking is the witness of place-names. Celtic _dunon_, a fort or castle (the Gaelic _dun_), is found in compound names from Ireland to Southern Russia. _Magos_, "a field," is met with in Britain, France, Switzerland, Prussia, Italy, and Austria. River and mountain names familiar in Britain occur on the Continent. The Pennine range of Cumberland has the same name as the Appenines. Rivers named for their inherent divinity, _devos_, are found in Britain and on the Continent--Dee, Deva, etc.