It might be a Scottish name, taken from a story about two men in a train. One man says, “What’s that package up there in the baggage rack?” And the other answers, “Oh that’s a McGuffin.” The first one asks, “What’s a McGuffin?” “Well,” the other man says, “It’s an apparatus for trapping lions in the Scottish Highlands.” The first man says, “But there are no lions in the Scottish Highlands,” and the other one answers “Well, then that’s no McGuffin!” So you see, a McGuffin is nothing at all.
~ Alfred Hitchcock gives a possible origin of the term to François Truffaut
Alfred Hitchcock popularized the term MacGuffin and used the particular plot element in many of his films. The MacGuffin is the valuable jewels, or the secret government papers, or the mysterious briefcase, or the Maltese Falcon. It could be anything. What’s important is what it means to the characters and how it motivates them to act. You might say the MacGuffin provides the occasion for the story.
MacGuffin should not be confused with McLovin.