This root was connected to fear and dread in Tolkien’s later writing, most notably in S. goroth as an element in S. Gorgoroth “[Valley] of Terror” as the name of a region in Mordor (LotR/401), as well as in S. Ered Gorgoroth “Mountains of Terror” where Ungoliant dwelled (S/95). The root first appeared in its extended form ᴹ√ÑGOROTH “horror” in The Etymologies of the 1930s (Ety/ÑGOROTH) with a variant ÑGOR-OT mentioned in another entry (EtyAC/GOS). The unextended root √ÑGOR was mentioned regularly in Tolkien’s later writings with glosses like “dread” (PE17/113), “terror, dread” (PE17/154), “fear” (PE17/172) and “terror” (PE17/183). It did not necessarily have an entirely negative meaning, however, as its derivative S. gorn given the sense “revered” in (one possible) etymology of S. Aragorn < Ara-ngorn “Revered King” (PE17/113).
A variant root √NGUR “horror” was mentioned in the Quendi and Eldar essay of 1959-60 (WJ/415), but elsewhere √ÑGUR was generally given the sense “death”; see that entry for detail.