Why are coming attractions of movies called trailers, especially when they come at the beginning of the film? They’re called that because they used to to be spliced on the end of the feature film.
To understand this, you have to hearken back to the days when movies were shown in a continuous loop and audiences were allowed to sit through multiple showings of the same movie—the start times were published and if you came in late you simply sat through the next showing until you came to the point “where you came in.” This is not that long ago—I remember when this used to be the practice.
The coming attractions reel would be spliced onto the end of the last reel of the movie, hence trailer. From the perspective of the audience member who arrived on time or a little early, the coming attractions would appear before the feature, even though technically it was at the end.
The term dates to the 1920s. From the New York Times of 11 March 1928:
A trailer, a few hundred feet of film announcing a forthcoming picture.
(Source: Oxford English Dictionary, 2nd Edition)
Copyright 1997-2013, by David Wilton