In recent times, Abracadabra has mostly been used by stage magicians. English mage Aleister Crowley (1875-1947) altered the spelling to make it fit his new magical religion of Thelema, and in this new form the word has been much used in the Thelemite community. See also Abrahadabra.
source: The New Encyclopedia of the Occult, John Michael Greer (Llewellyn Publications)
Abracadabra: The spelling of the word was changed by Aleister Crowley to “Abrahadabra” to place the name Had, the second person of Crowley’s Thelemite trinity, at the center. Abracadabra is traditional outside the Thelemite community.
Some people have tried to associate the word with ancient Jewish mysticism and Kabalism. Typical examples say that it is derived from ab, ben, and ruach acadasch, words that respectively mean father, son, and Holy Spirit. Another supposed source is ...
Readers familiar with the writings of Aleister Crowley will recognize the somewhat unusual spelling of the word "MAGICK." Crowley did this to distinguish Occult "Magick" from the "magic" of legerdemain, and also to separate the new Occult Magick ...