Night Fever by The Bee Gees-
When Bee Gees manager Robert Stigwood was producing a movie about a New York disco scene, the working title for the film at that time was Saturday Night. Stigwood asked the group to write a song using that name as a title, but the Bee Gees disliked it. They had already written a song called "Night Fever", so the group convinced Stigwood to use that and change the film to Saturday Night Fever.