Preview movie trailer called because it was originally shown after announcements of films

Advertising announcement next movie is called "trailer". However, the main value of the English verb trail is "follow the trail", that is the logic of trailers must not precede the main movie, as it is in modern cinema, and to follow at the end of it. That's how things were in 1912, when the first trailer, but soon realized the futility of the distributors of such an approach, as the bulk of the audience left the place after the final credits, and did not want to watch the news. Then it was decided to show the trailers at the beginning of the session, and the term is already entrenched in the language.

via factroom.ru