Surname derived from the name Day or Diego, for this reason does not have a common origin.

Older members of the lineage of which are known come from Leon.

There is another branch of the lineage in the Lordship of Molina, who descends from Alphonso Diaz one of the three hundred knights who fought in the reconquest of Moorish territories in ocuapados by Baeza.

Many branches of noble lineage test his military orders to enter at Valladolid and Granada.

Can not forget Rodrigo Diaz de Vivar the famous "El Cid" de Vivar refers to the birthplace Vivar Castle, the town of the same name, which was owned by his father, the Count Don Diego Lainez in the province Burgos.

Are widespread in America, one of the most prominent and oldest in the new continent is the chronicler Bernal Diaz del Castillo, who in 1514 embarked for America. First in Cuba participated in the first expeditions to Mexico with Francisco Hernandez de Cordoba, and later with the same Hernan Cortez.