Orc I think was original to Tolkien, but derived from Old English for giants and ogres.
Many others, like uruk-hai and hobbit, were original.
Also, even though some of the races come from Norse mythology, Tolkien's description of them and their habits are unique (and many times quite different from the "sources").
These two facts converge to make claims of originality very strange and difficult, because the derivations themselves are examples of original work.
Tolkien came up with new stories and characters, but the style is similar (and of course with sources from Norse Mythology and others, that mixed and grew apart, etc)
http://www.amazon.com/The-Road-Middle-Earth-Tolkien-Mytholog...
I haven't yet read Shippey's "Author of the Century", which is about a second set of influences (like the World Wars).
For more background, Tolkien was heavily inspired by - among other material - a compilation of Finnish oral tradition called "Kalevala". I've read that he used to complain that the English culture lacked such a tradition which most certainly lead to what the Silmarillion, The Hobbit, The Lord of the rings and everything else.
I forgot the exact term, googled the one I used, saw it was a thing, and assumed I had remembered it correctly. :( My bad.
http://en.wikipedia.org/wiki/Hobbit_(word)#Evidence_of_earli...
OED has not, even after all this time, granted him "invention" of the term, despite long inquiries into its origins.