What is "chapeauroux"

The Chapeauroux is a long river in the Lozère and Haute-Loire départements, south-central France. Its source is near Estables, in the Margeride. It flows generally northeast. It is a left tributary of the Allier into which it flows between Saint-Bonnet-de-Montauroux and Saint-Christophe-d'Allier.