In the spring 56 BC during the Gallic wars and according to Caesar, the Namnetes allied to the Veneti to fight against the fleet made by Caesar. Decimus Brutus, leader of the Roman fleet, finally won the battle.
During Roman domination, the Namnete capital city was located at the confluence of the Loire and the Erdre; its name was probably Condevicnum. During the 3rd century AD, the city became known as Portus Namnetum, then Nantes in the Middle Ages.
According to Strabo, quoting Poseidonios, there is an island in the Ocean near the outlet of the Loire river which was inhabited by the "women of the Samnitae," which is generally taken to be a mistake and actually refers to the "Namnitae" or Namnetes. No man was ever allowed on the island and the women themselves sailed from it to have intercourse with men on the continent before returning there again. They also had the strange custom of unroofing their temple every year and roofing it again on the same day before sunset, each woman bringing her load to add to the roof. The woman whose load would fall out of her arms was rent to pieces by the rest, and they allegedly carried the pieces round the temple with the cry of "Ev-ah" in a frenetic manner.
According to French archaeologist Jean-Louis Brunaux, there are three reasons to consider the story as factual. First, the wet and windy climate of Western Gaul suggest that the Gallic dwellings (made of branches or reed) were re-roofed every year. Second, not to drop new material was, according to Pliny the Elder, a common religious practice of the Celts. Third, circumambulation existed as a rite among the Celts according to Poseidonios.