A Boggart is an amortal non-being best known for its ability to shapeshift into the form of the viewer’s worst fear. A bogart’s true form is unknown, as its shapeshifting ability is instantaneous once it is viewed.
It is unknown when boggarts came into existence, as they are amortal non-beings, they are not alive, and though they can be made to vanish, they cannot be killed. There are several famous boggarts on record, one of the earliest being the Old Boggle of Canterbury which the Muggles had believed to be a cannibalistic hermit living in a cave, but the small boggart had been using the caves echoes to cause fear in those nearby. Another famous boggart was the Bludgeoning Boggart of Old London Town, this boggart had taken the form of a murderous thug in the early 19th century in London, but with a simple incantation could be turned into a hamster. A famous Scottish boggart was the Screaming Bogey of Strathtully, this boggart fed on the fears of Muggles in the area so heavily it had become a gargantuan black shadow with glowing white eyes, this boggart was, in time, trapped in a matchbox by Lyall Lupin of the Ministry of Magic.
The name boggart is similar to some early Celtic mythology terms (bogart, bogan, bogle, or boggle), and was thought to be a mischievous household spirit. It is unknown which term came first.