Abracadabra

Abracadabra is a magic word, historically used as an apotropaic incantation on amulets and common today in stage magic. It is of unknown origin.

Etymology
Abracadabra is of unknown origin, but according to the Oxford English Dictionary, its first known occurrence is in a second-century work of Serenus Sammonicus (see below).

Several folk etymologies are associated with the word: from phrases in Hebrew that mean "I will create as I speak", or Aramaic "I create like the word" (אברא כדברא), to folk etymologies that point to similar words in Latin and Greek such as abraxas or to its similarity to the first four letters of the Greek alphabet (alpha-beta-gamma-delta or ΑΒΓΔ). According to the OED Online, "no documentation has been found to support any of the various conjectures."

Historian Don Skemer suggests that the word could originate from the Hebrew phrase “ha brachah dabarah”, which means "name of the blessed", which was said to be a magical phrase.

Professional Aramaic linguist Steve Caruso argues that Abracadabra can neither be Aramaic nor Hebrew, and suggests that the popularisation of the mistaken etymology is a result of an extended discussion on an early internet message board, which credits rabbi Lawrence Kushner with publishing a modern etymology.

History
The first known mention of the word was in the second century AD in a book called Liber Medicinalis (sometimes known as De Medicina Praecepta Saluberrima) by Serenus Sammonicus, physician to the Roman emperor Caracalla, who in chapter 52 prescribed that malaria sufferers wear an amulet containing Abracadabra written in the form of a triangle.

The power of the amulet, he claimed, makes lethal diseases go away. Other Roman emperors, including Geta and Severus Alexander, were followers of the medical teachings of Serenus Sammonicus and may have used the incantation as well.

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.

A Jewish codex from 16th century Italy entitled as Ets ha-Da’at ('The Tree of Knowledge'), described as a collection of magical spells, contains the word for an amulet. It was described as a "cure from heavens" for "all sorts of fever[s]", consumption, and fire.

The Puritan minister Increase Mather dismissed the word as bereft of power. Daniel Defoe also wrote dismissively about Londoners who posted the word on their doorways to ward off sickness during the Great Plague of London.

The religion of Thelema speaks of the word 'Abrahadabra', and considers it the magical formula of the current Aeon. The religion's founder, Aleister Crowley (1875–1947), explains in his essay Gematria that he discovered the word (and his spelling) by qabalistic methods. The word 'Abrahadabra' also appears repeatedly in the 1904 invocation of Horus that led to the founding of Thelema (The Equinox I, no. 7. 1912).

In the early 1800s the word was used as an example of what magicians would say. Abracadabra is now more commonly used in the performance of stage magic as a magic word at the culmination of a trick.