The Historia Compostelana says St James (Sant'Iago in Spanish) was buried at Santiago de Compostela. He appeared to fight for Christians against the Moors at the battle of Clavijo, 844, thus called Matamoros (Moor-slayer). "Santiago y cierra España" ("St James and strike for Spain") is the battle cry of Spaniards: "St James the Moorslayer, one of the most valiant saints and knights... has been given by God to Spain for its patron and protection." (Cervantes, Don Quixote). Shakespeare adds the Spanish name of Iago to his source from such anti-Moorish associations, suggesting motivations which are not merely private.
The name Moor pre-dates Islam, from the Kingdom of Maure, Roman Mauretania, now partly Morocco. Latin "maurus" means "from Mauretania" so "Moors" could be Berbers, Arabs,even Muslim Iberians. Moro is used for dark things, so the Milanese Duke Ludovico Sforza was called Il Moro for his dark complexion. In Iberia, "moura" may refer to supernatural beings, having magical powers, and unbaptised, not Christian. In 711 Islamic Moors conquered Visigothic Christian Hispania. By 1212, Christian kings drove the Muslims from central Iberia. In 1492 the last Muslim kingdom of Granada surrendered to Ferdinand and Isabella who forced Muslims and Jews either to leave Spain, convert to Christianity or be killed. Under the Inquisition some Muslims converted reluctantly. Doubts about Othello's commitment to Christianity may be reinforced by his lack of mercy to Desdemona and himself, like the initial harshness of pagans such as Lear, Coriolanus, or Leontes.
Othello's origins are unnamed, but his "royal" background might fit an elitist Iberian Arab better than a tropical African's, as Olivier portrayed him, for his Christianity fits the later complexities of Iberian history. There is a hint of this when he says:"I have another weapon in this chamber,/ It is a sword of Spain, the ice brook's temper:"(V.ii.314-5). The sound "o telo" in classical Greek approximates to "the distant" i.e. "the alien" (cp. telephone: far sound) but other conjectures abound about the name's origin. Picture by Juan de Flandres (15th c.).
[Data courtesy of the Yorck Project, under Creative Commons Attribution-Share- Alike License (Wikipedia)]