"Abracadabra" is of semitic origin. It is my understanding that it comes from Aramaic, not from Hebrew but I could be wrong . Abra, however, comes from "bara" (Shoshana, if you are there, would you give the infinitive?) to make or create (as in the opening verses of Genesis: "Bareishit bara Elokim" (in the beginning God made...") The alef (here the vowel 'ah') is [a] future tense of the first person singular (Shoshana, please verify and tweak). The meaning of the expression is, approximately, "I will make as according to your word[s]"

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