He had several aliases

Around 1045, in the town of Vivar in the Castilian principality close to Burgos, Spain, Rodrigo Dáz de Vivar or Ruy Dáz de Vivar was born. Diego Lainez, his father, served as a soldier in the battle of Atapuerco in 1054 between King Garcia Sánchez III of Navarre and King Ferdinand I of León. According to certain historians, Diego was a progeny of Lain Calvo, a renowned duumvir (magistrate) in the Court of Ordo II (King of Galacia, who reigned from 914 to 924). Rodrigo's mother whose name is unknown was a niece of the Spanish minister Nuo Alvarez de Carazo. She gave her baby the name Rodrigo in honor of her father.

When Rodrigo Daz de Vivar was born, the southern two-thirds of the Iberian peninsula had been mostly captured by Islamic armies as part of the Arab conquest that had started in the eighth century CE. Around 1045, in the town of Vivar in the Castilian principality close to Burgos Spain, Rodrigo was born. One of the interesting facts about El Cid is he had several aliases. His full name, Rodrigo Diaz de Vivar or Ruy Díaz de Vivar, and the Moors' (Arabs living in medieval Spain) nickname of El Cid, which translates to "The Lord," have previously been mentioned, but he also went by a few other names. If Rodrigo was too formal for someone, they might call him Ruy, the moniker he goes by in an anime from the 1980s about El Cid's youth. The Christians dubbed him El Campeador, Spanish for "The Battlefield" or "The Warrior," whilst the Moors referred to him as El Cid. He had to be a brutal warrior to obtain such a title.