ROMA – That Aramaic was the lingua franca of a vast area of the ancient Middle East is a notion that is by now amply noted by a vast public, thanks to Mel Gibson’s film “The Passion of the Christ,” which everyone watches in that language. But that Syro-Aramaic was also the root of the Koran, and of the Koran of a primitive Christian system, is a more specialized notion, an almost clandestine one. And it’s more than a little dangerous. The author of the most important book on the subject – a German professor of ancient Semitic and...