Meaning of hagib by Pablo

The word Hagib or Jayib is used interchangeably by different authors, so I think that you can write in one way or another. In the case of the first category "Hagib", where here it is said that it is wrong, we can find it in many texts by renowned authors. I quote some:-XAVIER BALLESTÍN. Doctor in history per the Universitat Autònoma de Barcelona and Almanzor specialist, in his work "Al - Mansur and the dawla ' amiriya" mentions HAGIB on several occasions. -RAUL ROMERO BARTOLOME, in his book "Hasday, the hagib of the Caliph" - REINHART DOZY (Arabist Dutch, 19th century), in his book "History of the Muslims of Spain" - JOSÉ ANTONIO CONDE, (Arabist 18th century), in his book "history of the domination of the Arabs in Spain "- memoirs of LA REAL ACADEMIA DE LA HISTORIA, volume 5 (posted 19th century) - historic old CASTILE geography of Pedro Murillo Velardo (spelled Hagib referring to Almanzor)." -The Duke of RIVAS also mentioned in one of his books "MORO EXPÓSITO" the word Hagib. -UNIVERSAL Chronicle of the Principality of Catalonia of Jerome Pujades. -THE counts of BARCELONA VINDICATED Bofarull Prospero.