“Trillera” is a flamenco style which is also called “cantes de trilla”, whose origin is folkloric. Specifically, the word “trilleras” comes from the popular songs associated with rural work. Melodically resemble to the “nanas” and its origin would be in Castilla. It is an old song, which was aflamencada (singing in the flamenco way) during the 19th century. They don't have any guitar accompaniment.
Its basic rhythm is with bells, reminding those who had to draft animals while threshing. This is complemented by “arrieras”. One of its most renowned performers was Bernardo el de los Lobitos.