This root served as the basis for Elvish words for “three” for much of Tolkien’s life. However, in its earliest appearance in the Qenya Lexicon of the 1910s, ᴱ√NELE was glossed “point” with derivatives like ᴱQ. neldor “beech”, ᴱQ. nele “tooth” and ᴱQ. nelt “corner”, while the derived numeral was ᴱQ. nelde “four” (QL/65). The contemporaneous Gnomish Lexicon also had G. nel “point, end, tip, jutting end” (GL/60), and G. deldron “beech” was almost certainly derived from a strengthened form of the root ndel- (PE11/8; GL/30). ᴱQ. nelde “three” first appeared in the Early Qenya Grammar of the 1920s (PE14/49, 82).
In the first layer of The Etymologies of the 1930s, this root was glossed “point, triangle” (EtyAC/NEL), but Tolkien changed the gloss of ᴹ√NEL to “three” and gave it two extended roots ᴹ√NELED (also “three”) and ᴹ√NELEK “tooth” (Ety/NEL, NELEK). In this revised paradigm, probably “tooth” was derived from the sense “triangle”. In The Etymologies of the 1930s, Ilk. neldor “beech” was still derived from this root, but was said to refer to the “three trunks” of Hirilorn.
In later writings from the 1950s and 60s, the gloss of √NEL was consistently “three” (WJ/421; VT42/24; VT47/10-11), and the extended form √NELED “three” appeared regularly as well (VT42/24; VT47/11). √NELEK “tooth” also appeared in several documents from the 1940s and 50s (PE19/58; PE21/56, 71).
Tolkien introduced ᴹ√EL as the basis for Elvish star-words in The Etymologies of the 1930s at the same time as he devised a new etymology for the words for “Elf” as the “Star-Folk” using an extended form of this root ᴹ√ELED (Ety/EL, ELED). The extended root √ELED seems to have survived at least up until around 1950, where it appear among list of examples of roots for Elvish tribal names, with deleted variant √EDEL (PE18/84). But later on the extended form seems to have fallen away, at least as the basis for Elf-words, being replaced in the Quendi and Eldar essay from 1959-60 by the root √DEL “walk, go, proceed, travel” and its Quenya-only variant √LED.
In the Quendi and Eldar essay, the words for “Elf” were recontextualized as a blend of the senses “star” and “departure”, referring to Elves both as the people of the stars and the specific group of the Eldar as those Elves who left for Aman (WJ/362-3). In these same notes Tolkien said that ele originated first as an interjection meaning “lo!, behold!”, as uttered when the Elves first beheld the stars (WJ/360). In this sense, it might have been a partial restoration of a (hypothetical) early root ✱ᴱ√ELE used for various words of wonderment and “otherness” in the 1910s and 20s; see that entry for details.