ARMORICA (AREMORICA)  , the Roman name, derived from two Celtic words meaning the " seaside " (ar, on, and mor, sea), for the land of the Armorici, roughly the peninsula of Brittany . At the time of the Roman advance on Gaul there were five principal tribes in Armorica, the Namneti, the Veneti, the Osismii, the Curiosolitae and the Redones . It was subdued by Caesar, who entirely destroyed the seafaring tribe of its south coast, the Veneti . Under the Empire it formed part of the province of Gallia Lugudunensis (Lugdunensis) . It contained hardly any towns, though many large country houses, and was perhaps less Romanized than the rest of Gaul . In and after the later part of the 5th century it received many Celtic immigrants from the British Isles, fleeing (it is said) from the Saxons; and the Celtic dialect which the Bretons still speak is thought to owe its origin to these immigrants .