The plain before Mordor (LotR/243), translated “Battle Plain” (S/292, TI/389), a combination of dagor “battle” and lad “plain” (SA/lad).
Conceptual Development: In Lord of the Rings drafts from the 1940s, this plain was first named N. Dagras, quickly changed to N. Dagorlad (TI/389).
dagor (“battle”) + lad (“plain, valley”)