The problem of the use of the word Ork (or Gork) is that this term was "coined" by Tolkien.
However, Tolkien used a term that already exists and adapting it to their needs and creating a characters with fantastic features.
But you don't have a picture/drawning of a Ork but only a name, so it's a different problem.
Anyway, It seems that ork
isn't copyrighted, so you can use this word.
We have indications of the term ork in the oldest writings in the greek-roman mythology, Orlando Furioso by Ariosto, in the Legend of Beowulf and many other fairy tales or stories of the past. (in some Ogre istead of Ork)
However, i think that your map contains explicit references to the Tolkien's work, causing an immediate connection between the word ork (ogre) and the Tolkien's ork.
This could be a problem,It would like to use the term Hobbit on the map, a term created by Tolkien and copyrighted.
But I am not of the opinion that the best solution is to delete the term Ork/Gork and replacing it with a more generic word like ogre.
I think that you should work on other elements in the map far more worrisome for the directy connection with Tolkien.
(The Two Towers, The Mount Doom).
I am in favour to suggest you to keep the term Gork (Ork/Ogre) but to remove/modify the connections to Tolkien (eg rename Mount doom , maybe Plains of doom
) and try to create an original world of fantasy without lose that magical feeling
that the stories of Tolkien have.
I think you're able to do that
Have a nice day