The name the Romans gave to the north-western peninsula of Gaul, what we now call Brittany and the French call Bretagne, which formed part of the Gallic conquests of Julius Caesar.
Following the arrival of the Saxons in Britain, sometime after 440 AD many Romano-Britains emigrated and settled in Armorica and northern Gaul. By 461 AD there was a British bishop attending a conference in Troyes and in 467 AD King Riothamus is recorded as having led a force of 12,000 men to assist the Romans against the Visigoths. We are therefore talking about fairly significant numbers and
it would be a reasonable conclusion to assume that it was the most pro-Roman, loyalist elements of Romano-British society that chose to leave.
This emigration appears to have been a fairly organised affair and carried out with the support of the local Roman authorities. The original Gallic Armoricans had shown a distressing tendency to rebel and it seems that the Romans welcomed an influx of a more dependable people.
There were further waves of emigration in the period 530 to 580 AD and the process did not really come to an end until 700 AD, by which time Armorica had became Bretagne, the land of the Britons, inhabited by a people that spoke Breton, a Brythonic Celtic variant similar to Welsh