Q From Harry W Hickey: The previews of coming attractions in movie theaters are generally called trailers, a term I have known from my childhood in the late 1930s. Why should they be called that? They do not trail behind the shows they are advertising; and (at least today) they invariably precede the main feature.
A An intriguing question, and one which needs a little delving into the history of the cinema to answer. I have seen it argued in all seriousness that a movie trailer is analogous to the scent trail of a drag race, so trailing an advertisement before the audience in the expectation (or, at least, the hope) that it will be followed. But the real story is more prosaic.
Back in the days when most film programmes were presented as double features, the piece of film advertising a forthcoming attraction was originally attached by the cinema projectionist to the end of the reel that contained the B feature or supporting film, so that it was shown between it and the main feature — so trailing the supporting film.
The origins of the movie trailer go back a long way. In 2007, the Straight Dope reported the Paramount executive Lou Harris as saying that the first trailer was screened at Rye Beach, a New York-area amusement park, in 1912:
One of the concessions hung up a white sheet and showed the serial The Adventures of Kathlyn. At the end of the reel Kathlyn was thrown in the lion’s den. After this “trailed” a piece of film asking Does she escape the lion’s pit? See next week’s thrilling chapter! Hence, the word trailer, an advertisement for a coming picture.
Los Angeles Times, 25 Oct. 1966.
A syndicated newspaper report a year later reported differently. This is from Wikipedia:
When Nils Granlund, the advertising manager for the Marcus Loew theater chain, produced a short promotional film for the musical The Pleasure Seekers, opening at the Winter Garden Theatre on Broadway. Loew adopted the practice, which was reported in a wire service story carried by the Lincoln, Nebraska Daily Star [on 9 November], describing it as “an entirely new and unique stunt”, and that “moving pictures of the rehearsals and other incidents connected with the production will be sent out in advance of the show, to be presented to the Loew’s picture houses and will take the place of much of the bill board advertising”.
However, the first recorded use of trailer for such short advertising films is from several years later, when the US had entered the First World War and war bonds known as Liberty Loan Bonds were being actively sold:
A committee of the National Association of the Motion Picture Industry yesterday began sending films known as trailers [advertising the bonds] to all of the 15,000 or more movie theatres in the United States. These films are seventy feet in length and will be attached to longer films that are shown at every performance.
New York Times, 2 Jun. 1917.
These days, as you say, when cinemas usually show just the one feature film, the trailers for forthcoming attractions have to be run before it to ensure a captive audience, so making the name puzzlingly inaccurate. However, it’s still the standard term within the industry, despite some success with attempts to replace it in the public’s mind with terms such as preview and coming attraction.
It’s more of a technological fossil than a linguistic one.