Abracadabra

ab-ra-ka-dab′ra, n. a cabbalistic word, written in succe ive lines, each shorter by a letter than the one above it, till the last letter A formed the apex of a triangle. It was worn as a charm for the cure of diseases. Now used generally for a spell or conjuring word: mere gibberish. [First found in 2d-cent. poem ( Præcepta de Medic in a ) by Q. Serenus Sammonicus; further origin unknown.]