Abracadabra, a cabalistic word used in incantations, and supposed to possess mystic powers of healing, especially when written in this triangular shape:

The paper on which this was written was to be folded so as to conceal the writing, stitched with white thread, and worn around the neck. It was a sovereign remedy for fever and ague. Possibly the virtue lay in the syllables Abra, which are twice repeated, and which are composed of the first letters of the Hebrew words signifying Father, Son, and Holy Spirit,--Ab, Ben, Rauch Acadosh. The earliest known occurrence of the word is in a poem of the second century, "Præcepta de Medicina," by Q. Serenus Sammonicus. It is now often used in the general sense of a spell, or pretended conjuring, jargon, or gibberish.