MacGuffin

In fiction, a MacGuffin (sometimes McGuffin) is an object, device, or event that is necessary to the plot and the motivation of the characters, but insignificant, unimportant, or irrelevant in itself. The term was originated by Angus MacPhail for film, adopted by Alfred Hitchcock, and later extended to a similar device in other fiction.

The MacGuffin technique is common in films, especially thrillers. Usually, the MacGuffin is revealed in the first act, and thereafter declines in importance. It can reappear at the climax of the story but may actually be forgotten by the end of the story. Multiple MacGuffins are sometimes derisively identified as plot coupons.

History and use
The use of a MacGuffin as a plot device predates the name MacGuffin. The Holy Grail of Arthurian legend has been cited as an early example of a MacGuffin. The Holy Grail is the desired object that is essential to initiate and advance the plot. The final disposition of the Grail is never revealed, suggesting that the object is not of significance in itself.

The World-War-I-era actress Pearl White used the term "weenie" to identify whatever object (a roll of film, a rare coin, expensive diamonds, etc.) impelled the heroes, and often the villains as well, to pursue each other through the convoluted plots of The Perils of Pauline and the other silent film serials in which she starred. In the 1930 detective novel The Maltese Falcon, a small statuette provides both the book's title and its motive for intrigue.

The name MacGuffin was coined by the English screenwriter Angus MacPhail and was popularized by Alfred Hitchcock in the 1930s.