Factual error: Keith Jennings refers to an astrologers' publication which describes a star "like the star of Bethlehem" but "on the other side of the world, the European continent." Bethlehem is not on the other side of the world from Europe, it's at the same longitude as eastern Europe and less than 800 miles from the European mainland. (01:00:20)
Factual error: Jennings says that the name of Megiddo derives from Armageddon and that it is south of Jerusalem. In actual fact, Megiddo is the source of the word Armageddon, not the other way around, and it is a long way north of Jerusalem. (01:26:30)
Factual error: In the cemetery, the skeleton of Gregory Peck's son is far too big to be that of a newborn, which it is supposed to be.
Factual error: It is highly unlikely that a British police detective making routine enquiries would be carrying a gun.
Factual error: In the opening scene, Gregory Peck is riding in the dark in a car in Rome on June 6th at 6:00am. The sun rises at 5:35am in Rome on June 6th.
Chosen answer: The idea wasn't entirely Hollywood's. The antichrist is sometimes said to be "born of a jackal. " Jackals are mentioned in the Bible, and some interpretations consider them a symbol of something that is "not of God." In the movie, it means that the kid was scary as hell, literally.
Hobbes