The consensus among linguists is that the ethnic name Belgae comes from the Proto-Celtic root *belg- or *bolg- meaning "to swell (particularly with anger/battle fury/etc.)", cognate with the Dutch adjective gebelgd "very angry" (weak

Caesar's book Commentarii de Bello Gallico begins: "All Gaul is divided into three parts, one of which the Belgae inhabit, the Aquitani another, those who in their own language are called Celts, in ours Gauls, the third. All these differ from each other in language,

Caesar conquered the Belgae, beginning in 57 BC. He writes that the Belgae were conspiring and arming themselves in response to his earlier conquests; to counter this threat, he raised two new legions and ordered his Gallic allies, the Aedui, to

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Julius Caesar describes Gaul at the time of his conquests (58–51 BC) as divided into three parts, inhabited by the Aquitani in the southwest, the Gauls of the biggest central part, who in their own language were called Celtae, and the Belgae in the north. Each of these three

Caesar names the following as Belgic tribes, which can be related to later Roman provinces:
Later,

Britain
The Belgae had made their way across the English Channel into southern Britain in Caesar's time. Caesar asserts they had first crossed the channel