Magister is an old medieval term for a Professor. It's been acquired in very recent years and thrown into the hopper as a sort of generic leader type for magical AD&D nonsense, probably because of confusing "magic" with "magisterial." Very long ago, both words came from the same root--Magi or Magians, the Zoroastrian religion that is regarded as the first monotheistic belief system of note. The later Muslims who converted (often, forcibly) the Magians of the MidEast demonized the religion, regarding Magians as infernal spell-users who had made contracts with the devil, Iblis. Hence, Magians become synonymous with spellcasting (magic) and all-encompassing knowledge (magisterial).
Well, you did ask.
