Some movies have a working title and the release is different. We may never know how many title drops are in those. Although we know that the working title for "The Dark Knight" was "Rory's First Kiss".
The working title of the project is often public, e.g. on signs to the location shoot, and as such is often cryptic so that that the casual observer won't know that e.g. "Rory's First Kiss" is a Batman movie.