why is a movie trailer called a trailer
Trailer (promotion) A trailer (also known as a preview or coming attraction) is a commercial advertisement for a feature film that will be exhibited in the future at a cinema, the result of creative and technical work. The term "trailer" comes from their having originally been shown at the end of a feature film screening.[1] That practice did not last long, because patrons tended to leave the theater after the films ended, but the name has stuck. Trailers are now shown before the film begins.
Fifth-wheel coupling The term fifth wheel comes from a similar coupling used on four-wheel horse-drawn carriages and wagons. The device allowed the front axle assembly to pivot in the horizontal plane, to facilitate turning. Basically a wheel was placed on the rear frame section of the truck, which back then only had four wheels; this wheel that was placed on the frame was the "fifth wheel", hence the name. The trailer needed to be raised so that the trailer's pin would be able to drop into the central hole of the fifth wheel.