Yes, if something is a registered trademark, the rules are clear. However, if a commom word or phrase is used, trademark registrars are not allowed to give them trademark status.
The guidelines are slightly different from country to country, but the common rule is "If a name is not associated with the product in the first place, but with something else, a trademark can be given only to the logo as picture, but not to the words".
As an example: If you name a movie "End of the World" you will never get a protection for the name. Prisoner of War is a common classification, you are most likely on the safe side here.