Riddermark

Riddermark or simply The Mark was the name among the Rohirrim for the land, more commonly known to outsiders as Rohan.

Etymology

Mark here is used in the sense of the "boundary mark" or "march". The original untranslated Rohirric term was Lôgrad or Rad.

J.R.R. Tolkien might have been inspired by William Morris's use of 'Mid-mark' in The House of the Wolfings, a novel by William Morris, which Tolkien owned and from which he took inspiration.