The Belgae are among the earliest inhabitants of the region of whom we have a record. At the time of the first Roman advance they were settled the region from the Seine and the Marne north to the mouth of the Rhine. We are told that the four tribes occupied what is now the Nord-Pas-de-Calais.
J Caesar records in 57 BCE that the Atrebates (the settlers, treb Gaulish "small settlement") occupied a region bounded by the Sensée to the east, the Clarence to the west and the Lys and the Deule to the north.
The Morini (the sea people) occupied the territory to the west of the Atrebates and north of the Ambiani from the Canche and up the coast to the Aa.
The Menapi occupied the coastal region beyond the Aa to the Rhine.
The Nervi were limited to the valleys of the Sensée and the Escault. Although Caesar counts the Nervi as a Belgic people, later writers note a strong Germanic strain in their make up.
Exactly what the ancient writers ment by Celtic, Belgic, or Germanic is far from clear. It is probably best to think of three zones, a western "Belgic" zone from Haute Normandie to the Rhine mouth, the central valley of the Aisne with the Remi and the Suessioni, and an eastern zone to the Rhine with a mixture of peoples and tribes closely linked to those on the right bank of that river.
Of the tribal capitals established by the Romans, three use the name of Augustus and the tribal name, three combine a Celtic root with the name of Caesar or Augustus. The others kept their Gaulish names and may predate the conquest.
Caesar mentions another seven important sites
There are many other old names from documents and inscriptions.