What are gwerziou in Breton oral literature?

In Breton literature, gwerziou (also spelled gwersiou) are narrative ballads in the Breton language that traditionally describe local events, history, legends, and folklore.12

These poems are a major form of oral literature and are characterized by their dramatic subject matter, which often includes crime, violence, historical occurrences, and encounters with the otherworldly—ranging from pagan figures like fairies to Christian figures such as saints and the Virgin Mary. Historically, these ballads were composed by people of all social classes and were frequently hawked at fairs as pamphlets.123

The gwerziou are distinct from sonioù, which are generally more focused on homely themes like love, nature, and daily work. One of the most significant collections of this genre was published by François-Marie Luzel in the late 19th century under the title Gwersiou Breiz-Izel.21