Abracadabra is an incantation used as a magic word in conjuring tricks that historically was believed to have healing powers when inscribed on an amulet. Abracadabra origin is thought to be from the Aramaic language. Abra=אברה which is "to create" and cadabra=כדברא which is "as I say", ultimately when merging the two words abracadabra means in Aramaic is create as I say thus used oftentimes in magic tricks.
The first known mention of the word ABRACADABRA was in the 2nd century CE in a book called Liber Medicinalis  (sometimes known as De Medicina Praecepta Saluberrima) by Quintus Serenus Sammonicus, physician to the Roman emperor Caracalla, who prescribed that malaria sufferers wear an amulet containing the word written in the form of a triangle:
A - B - R - A - C - A - D - A - B - R - A
A - B - R - A - C - A - D - A - B - R
A - B - R - A - C - A - D - A - B
A - B - R - A - C - A - D - A
A - B - R - A - C - A - D
A - B - R - A - C - A
A - B - R - A - C
A - B - R - A
A - B - R
A - B
This, he explained, diminishes the hold over the patient of the spirit of the disease. Other Roman emperors, including Geta and Alexander Severus, were followers of the medical teachings of Serenus Sammonicus and are likely to have used the incantation as well.
According to the 1911 Encyclopædia Britannica it was used as a magical formula by the Gnostics of the sect of Basilides in invoking the aid of beneficent spirits against disease and misfortune. It is found on Abraxas stones which were worn as amulets. Subsequently its use spread beyond the Gnostics, and in modern times it is applied contemptuously to a conception or hypothesis which purports to be a simple solution of apparently insoluble phenomena.
The word is now commonly used as an incantation by stage magicians.
In popular culture
The expression "Avada Kedavra" is used as lethal spell known as Killing Curse in the Harry Potter series. During an audience interview at the Edinburgh Book Festival on 15 April 2004, the series author J. K. Rowling had this to say about the fictional Killing Curse's etymology: "Does anyone know where avada kedavra came from? It is an ancient spell in Aramaic, and it is the original of abracadabra, which means 'let the thing be destroyed.' Originally, it was used to cure illness and the 'thing' was the illness, but I decided to make it the 'thing' as in the person standing in front of me. I take a lot of liberties with things like that. I twist them round and make them mine."
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