Rohir is a Gondorian term for, I think, "horserider". That's off the top of my head. But rest assured, Tolkien coined the word.
The "Rohirrim" refer to themselves as the Eorlingas. Singular: Eorling.
By the way, Gwath, Eodwine is about 6 ft one inch, Whereas Harreld is 6 ft 4, and bigger of build.