In the movie one of allien races will be called Orcs. Is that right because as far as I know there is dozens of movies and games that use orcs as their race name and they are all almost the same.
Literaly, if you use something very exclusive of something you got inspired by, it is trouble, but, if you use something that is not exclusive to the forgery, you are all set at the very basic sense totaly.
Orcs are not exclusive, even Ogres are not exclusive (to Tolkien, etc). But as it has been mentioned, Klingons are exclusive subject, originaly defined and described in Star Trek series.
If some of situations and happenings get similiar to some other happenings and situations, this is out of question too I'd very strongly assure- there is no patent for being hit, stolen from, or blowen the monastery from :)
You should explore the exclusivity of things you wish to have. But in general, 100+ years existence of a thing, means it is not copyrighted or authorized, wheather it is Davinci's Michelangelo, or the Basilic of St. Peter, etc., (though catholic church may get uncomfortable by some iritating usage, but since we are not in any fundamental society, it'd be imposible to persecute you in any legal manner)