Armorica

Armorica or Aremorica is the name given in ancient times to the part of Gaul between the Seine and Loire rivers, that includes the Brittany peninsula, extending inland to an indeterminate point and down the Atlantic coast. The toponym is based on the Gaulish phrase are-mori "on/at [the] sea", made into the Gaulish place name Aremorica (*are-mor-ika ) "Place by the Sea". The suffix -ika was first used to create adjectival forms and then, names (see regions such as Pays d'Ouche from Utica and Perche from Pertica). The original designation was vague, including a large part of what became Normandy in the 10th century and, in some interpretations, the whole of the coast down to the Garonne river. Later, the term became restricted to Brittany.

In Breton (which belongs to the Brythonic branch of the Insular Celtic languages, along with Welsh and Cornish), "on [the] sea" is war vor (Welsh ar fôr – "f" being voiced, as "v" is in English), though the older form arvor is used to refer to the coastal regions of Brittany, in contrast to argoad (ar "on/at", coad "forest" [Welsh ar goed (coed "trees")]) for the inland regions. These cognate modern usages suggest that the Romans first contacted coastal people in the inland region and assumed that the regional name Aremorica referred to the whole area, both coastal and inland.

Pliny the Elder, in his Natural History (4.17.105), claims that Armorica was the older name for Aquitania, stating Armorica's southern boundary extended to the Pyrenees. Taking into account the Gaulish origin of the name, this is perfectly correct and logical, as Aremorica is not a 'country name', but a word that describes a type of geographical region - a region that is by the sea. Pliny lists the following Celtic tribes as living in the area: the Aedui and Carnuteni as having treaties with Rome; the Meldi and Secusiani as having some measure of independence; and the Boii, Senones, Aulerci (both the Eburovices and Cenomani), the Parisii, Tricasses, Andicavi, Viducasses, Bodiocasses, Veneti, Coriosvelites, Diablinti, Rhedones, Turones, and the Atseui.

...
Wikipedia