ATMachine said:
And as far as that last point goes: even Tolkien wasn't above renaming somebody else's character and reusing him. ... ...
And King Théoden himself was named after the protagonist of a late 19th century William Morris novel: a Germanic chieftain named Thiodolf, who dies valiantly repelling an assault by a Roman legion.
BTW, Theoden is Old English for "King." So... no.