Wrap is a phrase used by the director in the early days of the film industry to signal the end of filming.
Since the 1920s, filmmakers have been using this phrase when filming is done and is ready to go into post-production.
After principal photography is concluded, it is traditional to hold a wrap party for the cast and crew of the film. This marks the end of the actors' collaboration (except for possible dubbing or pick-ups) on the film. They may be called in to promote the film when it is released.
The term "wrap" is sometimes said to be an acronym for "Wind, Reel and Print", although this is disputed, and most likely a backronym. When purchasing meat products before they are taken away by the consumer for sanitary reasons they are wrapped before being taken away by the consumer. Likewise a completed motion picture is the "meat" of the film and to mark that it is ready for the consumer a director simply calls out "It" a wrap" meaning it is ready for "the consumer".