Sindarin name of Isengard (LotR/473), a combination of angren “iron” and ost “fortress” (SA/anga, os(t); PE17/32).
Conceptual Development: In Lord of the Rings drafts from the 1940s, this name first appeared as N. Angrobel (TI/71), variously revised to N. Angost or Angrenost (TI/420; WR/44, 72), eventually settling on the latter.
Sindarin name of the river Isen (UT/318), it is simply the adjective angren “iron” used as a name.