§ Hebel ?Orolos >> Hebel Uilos Nimr[?ais] (WR:137)
§ Ephel Nimras >> Ephel Nimrais, Ered Nimrath (WR:137,156)
§ Ered Nimras (WR:167-168)
At this point the ’Black Mountains’ (see Ered Myrn, Eredvyrn, Mornvenniath above (2.15)) were changed to ’White Mountains’ with several Elvish experimental forms. The ultimate form became Ered Nimrais ’White-horn mountains’ (UT:436).
Hebel did already occur in Hebel Dúath as a name for a mountain range (also Ephel, see 3.12). The form ?Orolos shows oro- from ORO- ’up, rise, high etc.’ either signifies something like *’height, mountain peak’, or plainly ’mountain’ as in Orofarne ’mountain-dwelling’ (Let:168). The second element is presumably lenited N. gloss ’snow, also adj. snow-white’. Thus Hebel Orolos *’Range of snow-white peaks’.
Uilos is a name elsewhere used for the Valinorean mountain Oiolosse ’Ever-snow-white’ (OY- UT:55, Rgeo:74), the initial element ui- comes from OY- ’ever, eternal’.
Nimr[?ais], if read correctly, is the plural of nimras ’white-horn’ < N. nimp, nim ’pale’ (NIK-W-) or nim ’white (usual word)’ < Telerin nimbı̆, alteration of nimpı̆ < *ninkwı̆ < NIK- (PE17:49,168) + *ras(s) or lenited ?rhass ’horn especially on living animal, but also applied to mountains’ (RAS-, VT46:10), of uncertain reading in The Etymologies (S. rass ’horn’ in PE17:36).
Interesting is Nimrath, which seems to contain rath ’course, riverbed’ (RAT-). On the other hand a later source cites rath- ’climb’ (UT:255) and rath, applied in Númenórean Sindarin to longer road-ways and streets of Minas Tirith (which were inclined), as Rath Dínen ’the Silent Street’. But a root meaning ’climb’ may also yield *’mountain’. Notable in this context is earlier Caradras ’Redway’ (see 1.10) with the roles of r(h)as and rath interchanged. So it may be that Tolkien just wavered concerning the application of these two words.