What exactly is a MacGuffin?

The term 'MacGuffin' is often misunderstood, being applied to any 'object of desire' in a film or book. For example, I recently came across a YouTube video were the presenter examined all the MacGuffins in the various Indiana Jones movies without apparently realising that none of the examples being used were actually MacGuffins at all.

In 'Indiana Jones and the Last Crusade' the object of desire is an anchient cup - the Holy Grail. But the Grail is not a MacGuffin because it plays an important part in the plot since, by virtue of it being the 'real Holy Grail, it saves the life of a major character. In contrast, a true MacGuffin does nothing at all. Beyond it being of value the MacGuffin is useless and unimportant.

My favourite example of a MacGuffin (and coincidentally the most prominent example on the Wikipedia page) is the Maltese Falcon, the eponymous MacGuffin of the 1941 noir movie directed by John Huston. The Maltese Falcon is valuable, but that's all it is. It doesn't matter that it's a statue of a falcon from Malta, those facts are not important to the plot. The Maltese Falcon could just as easily have been a rare stamp, valuable coin or old master painting. You could have called the movie 'The Golden Gibbon' or 'The Diamond Dentures'.

That is the true test of the MacGuffin: beyond being worth something to the people chasing it, if it can be replaced by absolutely anything else, it's a MacGuffin.

I've even heard the One Ring being referred to as a MacGuffin. A ring that can turn you invisible, summons the Nazgul, and makes the its owner the most powerful being on Middle Earth. It's probably the least 'MacGuffingy' thing imaginable.

Where the term actually came from is not clear, but Alfred Hitchcock had this theory:

It might be a Scottish name, taken from a story about two men on a train. One man says, "What's that package up there in the baggage rack?" And the other answers, "Oh, that's a MacGuffin." The first one asks, "What's a MacGuffin?" "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 MacGuffin!" So you see that a MacGuffin is actually nothing at all.