Magister

"Magister" was, according to the Third Doctor, "the Latin word for Master". When used the word as an alias, the Doctor immediately realised his nemesis' involvement. Olive Hawthorne instead recognised the name as being given to "the leader of a black magic coven". Jo Grant, on the other hand, had never heard the word in her life. (TV: The Dæmons)

during the Time War again used the Magister alias while posing as a village priest in the 1940s, as "Reverent Magister". (AUDIO: The Survivor) Later still, called herself "Miss Magister" while working as a schoolteacher at a boarding school. (PROSE: Yes, Missy)