Elective Semantectomy

The Elective Semantectomy was a temporal engineering procedure by which a member of the Great Houses could remove their true name from history and replace it with an impersonal title of their choosing.

Nature
In most cases, this was done to protect a bloodline from embarrassment due to association with a renegade member, (PROSE: Weapons Grade Snake Oil) as the full names of many Houseworlders included the name of their Great House. (PROSE: Lungbarrow, The Book of the War, Against Nature, AUDIO: Body Politic, Panacea)

By one account, names held mystic importance in Time Lord society, meaning that all Time Lords kept their true names as closely-guarded secrets. In this sense, the Doctor's name was not any more or less significant than any other Time Lord's. (PROSE: Doctor Who and the Terror of the Autons)

The Doctor
The most notable, but far from the only Renegade Time Lord whose name was in the form of an impersonal title was the Doctor, (TV: An Unearthly Child) who was alternatively known as the Warrior, (PROSE: The Stranger) the Valeyard, (TV: The Ultimate Foe) the Emperor, (PROSE: Father Time) and the Curator, (TV: The Day of the Doctor) with other aspects including the Watcher (TV: Logopolis) and the Dream Lord. (TV: Amy's Choice) The Eleventh Doctor claimed that he had chose the title as a promise, (TV: The Name of the Doctor) which would be adopted by other individuals. (TV: Flatline)

Before the Doctor left Gallifrey, he and the Master erased their names from history in the "names experiment" so that only they remembered, (AUDIO: Blood of the Time Lords) the Doctor having broke his name into thirty-eight pieces. During his travels, he spread them throughout the universe. (PROSE: Return of the Living Dad) In one of the versions of the Doctor's past, the Doctor's father erased both of their names from history. (PROSE: Unnatural History)

Accounts of the Doctor's early life before the First Doctor had them known as the Other, (PROSE: Lungbarrow) the Stranger (AUDIO: Patience) or the Doctor, (TV: Fugitive of the Judoon, The Timeless Children) with one account having the unidentified individual who would eventually become the Doctor being found by a Gallifreyan explorer, becoming known as the Timeless Child. (TV: The Timeless Children)

After altering his memories, the Great Houses made Chris Cwej believe that he had travelled with a fictitious malevolent renegade who intentionally called himself "the Evil Renegade", (PROSE: Dead Romance) instead of the Seventh Doctor. (PROSE: Original Sin, etc.)

Other cases
Other such Renegades included the Monk, (TV: The Time Meddler) the Master, (TV: Terror of the Autons) the Rani, (TV: The Mark of the Rani) Morbius during his time as the General, (PROSE: Warmonger) the Interfering Nun, (PROSE: Shada) the Colonel, (PROSE: CIA File Extracts) the Grandfather, (PROSE: Interference, The Book of the War) the Imperator, the War King, (PROSE: The Book of the War) the Hussar, (PROSE: Weapons Grade Snake Oil) the Clocksmith, (AUDIO: The Eighth Piece) the Magician, (PROSE: Turlough and the Earthlink Dilemma) the Eleven, (AUDIO: The Eleven) the Corsair, (TV: The Doctor's Wife) and the Corsair, (PROSE: The Bloodletters) the Heretic, (AUDIO: The Two Masters) the Player, (AUDIO: The Plague of Dreams) and the Dark Citizen. (AUDIO: Dark Universe) The Time Lord originally known as Caleera became the Sonomancer and later the Red Lady. (AUDIO: Scenes From Her Life, The Sonomancer, The Red Lady)

By some accounts, the Doctor knew a hermit as the Hermit. (PROSE: Timewyrm: Revelation, Lucifer Rising)

Some of the first members of the Great Houses to shed their names and take on new ones were actually the Mappers who first explored the Spiral Politic after the anchoring of the thread, who all went insane sometime after finishing their work. However, instead of the "titles and stuff" which typified later Renegades, they chose "really stupid names" (in Intrepid's opinion) based on a timekeeping theme, such as Astrolabe or Pendulum. (PROSE: Going Once, Going Twice)

Morbius, sometimes considered the "First Renegade", (PROSE: Still Need a Title!) operated under the name of "the General" during his exile from Gallifrey in his first incarnation. This allowed Gallifrey a window of plausible deniability about whether "the General's" intergalactic crimes were Gallifrey's responsibility, and thus, whether they had a duty to intervene. Eventually, however, the Doctor convinced them that the General and Morbius were one and the same, and they sent him to intervene. (PROSE: Warmonger) After his execution and survival, the tyrant returned to calling himself simply "Morbius". (TV: The Brain of Morbius, AUDIO: The Vengeance of Morbius)

According to a guide to Gallifreyan history written by a temporal tourism tour operator in the post-War universe, the "figurehead Lord President" who stood in for Romana II after her disappearance was in fact "un-named", and not merely obscure. (PROSE: Gallifrey: A Rough Guide)

During the War in Heaven, some Homeworlders volunteered to undergo Semantectomy before being stationed among the lesser species, due to fears that adopting a local name might lead to conceptual contamination. (PROSE: Weapons Grade Snake Oil) Likewise, during the Last Great Time War, Time Lords very much in service of orthodox Gallifrey were also known to bear such "titles" instead of ordinary names, including the Visionary (TV: The End of Time) and the General. (TV: Hell Bent) Even before the Time War, K9 Mark I's overseer in Gallifrey High Command was known as simply the Space Controller (PROSE: K9 and the Zeta Rescue) and the overseer of the Cartago colony was simply "the Governor". The Monk was also known as such even before he "turned Renegade". (PROSE: The Bloodletters)

After the Woman and the Patriarch of Stillhaven dissented to 's plan for the Ultimate Sanction during the Last Great Time War, (TV: The End of Time, PROSE: Lords and Masters) Rassilon had the Woman's name erased from time. (PROSE: A Brief History of Time Lords)

Professor H Lennistein wrote about the Elective Semantectomy in his 31441 book The Great Houses And Us. (PROSE: Weapons Grade Snake Oil)

When River Song expressed scepticism as to the Eleventh Doctor's uncle being known simply as the Uncle, the Doctor described it as "a Time Lord thing." (GAME: The Eternity Clock)

Behind the scenes

 * In an interview in DWM 490, Steven Moffat proposed that Dr. Who recklessly altering Time to change the outcome of the bank robbery at the end of Daleks' Invasion Earth 2150 A.D. caused him to accidentally restart the universe, rewriting himself into a Time Lord and losing his family name.