The Gallo-Celtic tribes bore the general appellation of Belgae, and among these the Nervii, inhabiting the district between the Scheldt and the Sambre were at the date of Caesar's invasion, 57 B.C., the most warlike and important.
The Treveri or Treviri, from whom the city derived its name, were one of the most powerful tribes among the Belgae, and according to Julius Caesar, who conquered them in 56 B.C., possessed the best cavalry.
According to this authority, Gaul was at that time divided among three peoples, more or less distinct from one another, the Aquitani, the Gauls, who called themselves Celts, and the Belgae.
In any case, only the eastern districts would have been affected by invaders from over the Rhine, the chief seat of the Belgae proper being in the west, the country occupied by the Bellovaci, Ambiani and Atrebates, to which it is probable (although the reading is uncertain) that Caesar gives the distinctive name Belgium (corresponding to the old provinces of Picardy and Artois).
Holmes (Caesar's Conquest of Gaul, 1899), who comes to the conclusion that "when the Reman delegates told Caesar that the Belgae were descended from the Germans, they probably only meant that the ancestors of the Belgic conquerors had formerly dwelt in Germany, and this is equally true of the ancestors of the Gauls who gave their name to the Celtae; but, on the other hand, it is quite possible that in the veins of some of the Belgae flowed the blood of genuine German forefathers."