Taboo

"Fear of a name increases fear of a thing itself."

- Albus Dumbledore to Harry Potter in 1992

The Taboo curse is a powerful spell which designates a word as a key to revealing the speaker's location. As such, it works in a similar manner to the Trace spell, but rather than being triggered when any magic at all is used, it is triggered by the speaking of a specific word. It also works regardless of the age of the speaker and regardless of any protective magical enchantments (except, seemingly, the Fidelius Charm). This curse controls individuals by limiting their freedom to speak, and thus causes great stress, terror, and frustration. Because of this, it may be considered to be Dark magic.

Use in the First Wizarding War
Throughout Harry Potter's childhood and adolescence, the spoken name of Lord Voldemort caused people to shiver in fear or cringe, as if Voldemort would appear in front of them, despite the widespread belief at the time that the Dark Lord was gone. Instead, he was referred to as "He-Who-Must-Not-Be-Named" and "You-Know-Who" by most. Even his followers, the Death Eaters, were afraid to use his name and called him the "Dark Lord." This could indicate that Voldemort placed the Taboo curse on his name during the First Wizarding War to inspire fear.

However given Dumbledore's efforts to get people to refer to Voldemort by his chosen name, it may simply be that Voldemort's actions were so terrifying that people became afraid to use his name. Had a taboo curse been placed on the name at the time it seems unlikely that Dumbledore would have wanted people to use the name, knowing it would allow Voldemort's followers to track down the users of the name.

Implementation
Sometime after seizing indirect control of the Ministry of Magic in 1997, Voldemort made his own name Taboo. Thus, whenever his name was spoken aloud, Death Eaters and Snatchers were alerted as to the location of the speaker. Since the only individuals who dared speak Voldemort's name were members of the Order of the Phoenix or their allies, the Taboo allowed Voldemort's followers to track down their enemies. Anyone who dares to speak the name and break the Taboo will be convicted and hunted down as criminals.

The anti-Voldemort radio programme Potterwatch, which was run by Order members and sympathisers, took to referring to Voldemort as "Chief Death Eater" as one of their methods of avoiding detection. .

Known triggers

 * Death Eaters Antonin Dolohov and Thorfinn Rowle used the Taboo curse to trace Harry Potter, Ron Weasley and Hermione Granger to a café on Tottenham Court Road shortly after they Disapparted from Bill Weasley and Fleur Delacour's wedding . The trio managed to escape. Although they did not know about the Taboo for some time, they stopped using Voldemort's name at Ron's request.
 * Death Eaters also used it to corner Kingsley Shacklebolt, but the Auror and Order member fought his way free and went on the run.
 * Harry Potter broke the Taboo in the spring of 1998, leading to the trio's capture by a gang of Snatchers led by Fenrir Greyback and subsequent detention at and escape from Malfoy Manor.

Possible triggers

 * The Taboo curse might have been responsible for the capture of Dean Thomas and Griphook, and the deaths of Ted Tonks, Dirk Cresswell, and Gornuk, at the hands of Snatchers.

Defence against the Taboo
The Taboo, when triggered can break normal defensive enchantments (invisibility, etc.) such as when Harry, Hermione, and Ron were captured by the Snatchers. However, when inside the protection of very powerful enchantments such as the Fidelius Charm, the protection seems to remain unchanged. This may be why the trio were protected at 12 Grimmauld Place, even though they repeatedly used Lord Voldemort's name while hiding there in 1997.

Appearances

 * Harry Potter and the Deathly Hallows

Notes and references
Tabou