§ Gorgoroth >> Narch Udûn (WR:438)
These were earlier names of the vale behind Morannon, called Udûn in The Lord of the Rings (LotRVI, ch.2).
The first name is simply N. Gorgoroth ’deadly fear’ (ÑGOROTH-).
Narch probably means *’cleft’ here, being from NÁRAK- ’tear, rend (tr. and intr.)’, compare Narchost ’bitter-biting fort’ (RC:601). N. Udun < Utubnu (TUB-) was originally Melkor’s northern fortress in The Silmarillion, compare also the entry tum of its index. Although not explicitly translated, it must have connotations with great deepness.