MacGuffin

The first person to use MacGuffin as a word for a plot device was Alfred Hitchcock. He borrowed it from an old shaggy-dog story in which some passengers on a train interrogate a fellow passenger carrying a large, strange-looking package. The fellow says the package contains a "MacGuffin," which, he explains, is used to catch tigers in the Scottish Highlands. When the group protests that there are no tigers in the Highlands, the passenger replies, "Well, then, this must not be a MacGuffin." Hitchcock apparently appreciated the way the mysterious package holds the audience's attention and builds suspense. He recognized that an audience anticipating a solution to a mystery will continue to follow the story even if the initial interest-grabber turns out to be irrelevant.