Conceptual Development: The earliest precursor of this name was G. Danigwethil, the Gnomish cognate of ᴱQ. Taniqetil in the Gnomish Lexicon from the 1910s (GL/29). This version of the name seems to be a combination of dâ “high” and nigweth “(snow) storm”, as suggested by Christopher Tolkien (LT1A/Taniquetil). This name had numerous variants, and evolved into ᴱN. Taingwethil in the Lays of Beleriand from the 1920s (LB/49, 135). A similar name TainBethil appeared in Early Noldorin notes from the same period as a combination of ᴱN. tain “mountain” and ᴱN. pethil (PE13/152); the later word was unglossed but was probably equivalent to the -qetil in ᴱQ. Taniqetil.
Starting with Tolkien’s writings in the 1930s, the usual Noldorin/Sindarin name for this mountain was Amon Uilos, cognate to its other Quenya name Oiolossë. He gave a few other Noldorin/Sindarin names, but none were direct cognates of Q. Taniquetil. In The Etymologies from the 1930s, he gave N. Nimdildor “High White Horn” derived from ᴹ✶Ninkwitil(di) Tára, a combination of Nimdil “White Horn” and taur “high” (Ety/NIK-W, TĀ). In the Quendi and Eldar essay from 1959-60 he gave the Sindarin form Ras-Arphain noted above (WJ/403).