The node form will not submit,if the word 'exit' is put in the title field
No, Drupal doesn't have any word blacklists.

That logic must be caused by a custom or contributed module that you have installed (or even a theme I suppose). Try methodically disabling modules/themes until you find the culprit.

Starting with modules that provide text filters or alter the content body in some way would be the obvious places to start.