From Tolkien Gateway

Firienfeld was what the Rohirrim called the flat upland of Dunharrow; a large grassy area for the encampment of soldiers and refuge-seekers.[1] Aragorn and the Grey Company passed through the Firienfeld on 8 March T.A. 3019; King Théoden and his riders arrived there the next day.[2]

Etymology[edit | edit source]

Firien represents Old English firgen, "mountain"; -feld, means "field" and Tolkien left it unmodernised; the Firienfield of the Index is in error.[3]