The most powerful spells used in the Dark Arts, these three curses go unmentioned until Harry Potter and the Goblet of Fire, when Mad Eye Moody introduces them to Harry and his classmates in their Defense against the Dark Arts class. They are forbidden by the Ministry of Magic and unforgivable because, as Hermione Granger explains, they are too horrific to tolerate.
The name itself says a lot about the curses, much as we muggles talk about unforgivable crimes. Use of any one of them is cause for imprisonment in Azkaban. The names of the three curses themselves are even more revealing.
The Cruciatus Curse
This curse is used to make someone feel intolerable amounts of pain. It is, in other words, a way to torture someone. Interestingly, the person who inflicts this curse must, according to Bellaxtrix Lestrange, want to do it for the sake of doing it. And the curse is cast using the word “crucio”.
Cruciatus means torture or torment in Latin. It comes from the verb cruciare, which means to torture or torment, physically or mentally. Crucio, meaning I torture or I torment, is from the cruciare, which is related to the Latin word crux, as in cross, but only insofar as crosses were used in crucifixion (lit.: put on a cross). Latin has several idioms with crux that mean torment: abi in malam crucem, for instance.
The Imperius Curse
This curse makes someone a puppet, under the complete control of the wielder of the curse. It is similar to being subjected to hypnosis, but of course magical and therefore more powerful. People can attempt to resist, as Harry did in Moody’s class. This curse is cast using the word “imperio”.
Imperius is not a Latin word, though imperio is from the noun imperium, meaning a command or order, and close to the verb imperito, meaning I command or I am in command, or impero, meaning I order, I give orders, or I command. These Latin words sound and feel familiar in English because of words like imperial, empire, emperor, and imperative.
This curse, also called the Killing Curse, is the worst of the three. This curse kills instantly and has no counter-curse or defense, though as Mad Eye Moody tells his Defense against the Dark Arts class, there is one person who survived it: Harry Potter.
Rowling was obviously inspired by the magic words “abracadabra” when she created the name of this curse. This phrase entered the English language around 1696 and came via Latin from the ancient Greek abraxas, a Gnostic or cabalistic name for the supreme god, and therefore a word of power. In ancient times the names of gods were routinely invoked as words of power. The individual letters were arranged in a pyramid and worn as a protective amulet.
The kedavra part of the curse also bears a phonetic similarity to the word cadaver, meaning dead body. The Romanian translation of the Harry Potter books reflects this similarity, and Rowling may have been inspired by it when she came up with the name of the Killing Curse.
Rowling, at the Edinburgh Book Festival in August, 2004, said that avada kedavra is an ancient spell in Aramaic meaning “let the thing be destroyed” and was used to cure diseases by destroying the illness. She turned this meaning around, she said, to make it her own.
In the The Magical Worlds of Harry Potter by David Colbert, the same explanation is given.
The name of this curse is related to the popular “mumbo-jumbo” magical phrase Abracadabra, which is actually of Aramaic origin: abhadda kedhabhra, meaning “disappear like this word”. Alternatively, the Aramaic words translate as “I create as I speak”.
Unfortunately, the Oxford English Dictionary and several other standard etymology dictionaries disagree. Wikipedia aslo cites as the source for the Aramaic origin, but this is a folk etymology that, so far, has no basis in linguistics or philology.
All that notwithstanding, the Unforgivable Curses are aptly named. Their use in Harry Potter and the Order of the Phoenix in the battle at the Ministry of Magic shows just how devastating they can be, and how the fear they inspire is justified.