N. Narch loc.
According to Christopher Tolkien, this was the initial name of the valley of Udûn in Mordor (SD/34), also appearing as Narch Udûn (WR/438). This name seems to have the same word narch seen in Narchost (the second of the Towers of the Teeth), but it isn’t clear whether J.R.R. Tolkien intended these names to be related.
References ✧ SD/34; SDI1/Narch; WRI/Narch Udûn