Men of Rohan
Men of Rohan
The descendant of Eorl and his followers
The Rohirrim; the Men of the Éothéod who came south to settle the Gondorian region of Calenardhon (renamed Rohan after their arrival) in the later part of the Third Age. They are a people of herdsmen and farmers who are well-known for their horses and cavalry. 
Horsemen of Rohan
A name given to the mounted soldiery of Rohan, known in their own tongue as the Éoherë, and in Elvish as the Rohirrim. This is a very rare name for these people, in fact used only once by Pippin in Minas Tirith, and so it may simply represent Pippin's ignorance of the proper titles for this people. 
The Horse-lords of Rohan
The Rohirrim were descended from the so-called Middle Peoples, Men who shared an ancient kinship with the ancestors of the Edain. Note that the detailed descent of the Northmen is rather more complex than shown here, and according to some readings the Rohirrim were ultimately descended from the 'Edain' branch of this tree. See the entry for 'Northmen' for a detailed discussion on this topic.
The people of Rohan. Originally descended from the Éothéod of the North. When Eorl was granted the land of Rohan, his people became known as the Rohirrim, from the Elvish for 'People of the Horse-lords'.