Aliases of the Master

Like the Doctor, the renegade Time Lord known as the Master used many aliases. However, while the Doctor used false names on a fairly ad hoc basis to avoid awkward questions, the Master usually adopted them in order to further whatever scheme they were embarked upon at the time, creating entire personas out of many of them.

"The Master" was itself an alias. He chose this name, as the First Doctor did his, while attending the Academy. (TV: The Sound of Drums; AUDIO: The Destination Wars)

True name
The Master's true name was spoken by a messenger to the Third Doctor as "a string of mellifluous syllables — one of the strange Time Lord names that are never disclosed to outsiders". (PROSE: Doctor Who and the Terror of the Autons) Missy claimed it had thirty-two letters. (PROSE: Lords and Masters) In one account, the Doctor and the Master both erased their names from history entirely as children, such that only they remembered it. (AUDIO: Blood of the Time Lords) The Celestial Intervention Agency's documents stated that the Master's real name had been purged from all Time Lord records after he and the Doctor left Gallifrey. (PROSE: CIA File Extracts)

Behind the scenes

 * During Anthony Ainley's tenure as the Master, pseudonyms made from anagrams of "Tony Ainley" were often used in the credits — both on-screen and in Radio Times — for the Master's disguises, such as Neil Toynay for the Portreeve in Castrovalva.
 * Another, craftier pseudonym was used in Radio Times for The King's Demons, when Sir Gilles was listed as being played by "James Stoker" — an anagram of "Master's Joke". This name was confirmed as an alias used by the Master in-universe at some point before the events of Planet of Fire in the novel CIA File Extracts.
 * In Sympathy for the Devil, Mark Gatiss, who voiced an alternate version of the Master, is credited as "Sam Kisgart", an anagram of the actor's name. When this incarnation of the Master returned in The New Adventures of Bernice Summerfield, Gatiss was again credited as Kisgart but the joke was dropped out for later stories.
 * In the previews of Ascension of the Cybermen, the Spy Master's return for the cliffhanger was foreshadowed by "Barack Stemis" being credited for a character called "Fakout" at the end of the cast-list. "Barak Stemis" is an anagram of "Master is back", while "Fakout" sounds like "fake-out".
 * In the DVD commentary for TV: The Lazarus Experiment, Mark Gatiss claimed that "Saxon" was an anagram of "Axons", made in reference to TV: The Claws of Axos.
 * Professor Stream in The Hollows of Time was originally intended to be a pseudonym of the "Tremas" Master, but copyright restrictions prevented them from making this explicit in the story. "Stream", like "Tremas", is an anagram of "Master". The story is listed as a Master one on the Big Finish website.