Breton was spoken in the
Middle Ages in a large area of the current department of
Loire-Atlantique, in the Guérande region, quite deep into the Nantais region, as far as
Lusanger,
Nort-sur-Erdre,
Vigneux-de-Bretagne,
Bouée and the coastal fringe of the
Pays de Retz. This maximum extension, determined by toponymy, dates back to the 9th century. Breton-Romance bilingualism was probably prevalent in many parts of this area. Subsequently, Breton gradually moved westward in favor of
Gallo, the
Oïl dialect spoken in
Upper Brittany. It is estimated that the linguistic boundary stabilized during the 12th century to the west of the
Brière marshes. Toponymy indicates the area where this boundary finally stabilized (place names in ker-). It is this territory that forms the traditional Guérande region, which, because of the language, belongs to Celtic Lower Brittany and not to Romance Upper Brittany. Closer to home, testimonies and documents allow us to know with near certainty the area where Breton is spoken in Loire-Atlantique: • 1695: The map by Jean-Baptiste Nolin indicates that Breton is still spoken to the west of a line including
Férel,
Herbignac,
Saint-Lyphard,
Guérande and
Le Pouliguen;
Saint-André-des-Eaux, Loire-Atlantique and
La Baule-Escoublac are in the Romance zone, but close to the Breton-Gallo border; • 1794: The French government decides by a decree of the national convention of the 8th day of Pluviôse of the year II that: "A French-speaking teacher will be established within ten days, starting from the date of publication of this decree, in each rural commune of the departments of Morbihan, Finistère, Côtes-du-Nord and in the part of Loire-Inférieure whose inhabitants speak the language called Bas-Breton;" • 1806: Coquebert de Montbret 's survey indicates that Breton is spoken south of the
Vilaine in Férel,
Camoël,
Pénestin. We also learn that Breton is still known in Bourg-de-Batz (Batz-sur-Mer), and that "the dividing line of the two languages begins at the salt marshes of Herbignac in the territory of the
Loire-Inférieure department [...]", that is, in the western part of the commune of
Assérac, as well as in part of
Saint-Molf, but probably also towards
Mesquer and
Piriac-sur-Mer. This survey did not concern the Loire-Inférieure department for administrative reasons. It is therefore very imprecise for the region that interests us; • mid- 19th century: According to a testimony collected by Paulin Benoist, some elders still spoke Breton in Piriac-sur-Mer after 1830 and in
Mesquer even later. In 1889, Canon Le Méné mentioned the disappearance of Breton in Pénestin "at a time quite close to ours"; • 1878: According to
Paul Sébillot, seven communes readily speak Breton and understand French. There are approximately 1,200 people who know it; • 1886: Sébillot's survey indicates that Breton, although extinct in all the other communes located south of the Vilaine, is still spoken in Bourg-de-Batz. This information is confirmed in 1887 by Alcide Leroux, who says that "in four villages of […] Bourg-de-Batz [… Kermoisan, Kervalet, Trégaté and Roffiat …], people aged 40 all know Breton"; he hears children playing in Breton in the streets of the village of Roffiat, proof of the vitality of the language; • 1911: in the Linguistic Atlas of Lower Brittany , it is indicated: “Bourg-de-Batz, Le Croisic, Loire-Inférieure, day laborer, 72 years old; only people of her age speak Breton well”. Batz-sur-Mer is therefore the last commune in the Pays Nantais to have spoken Breton. ==Disappearance==