This root and ones like it were the basis for Elvish “man” words for much of Tolkien’s life. The earliest form of this root was ᴱ√NERE with derivatives like ᴱQ. ner “man, husband” and ᴱQ. nertu “strength” (QL/65). The latter had a cognate G. nert in contemporaneous Gnomish Lexicon, along with a set of related “strength” words (GL/60). But Gnomish also had a set of derivatives based on the elided primitive form ᴱ✶n’reu̯ such as G. †drio “hero” and driog “valiant” (GL/30). Derivatives with an initial n- continued to appear in Early Noldorin word lists from the 1920s, such as ᴱN. †nîr “hero, prince” and ᴱN. ne(i)rion “hero” (PE13/164).
In The Etymologies of the 1930s, the base root was ᴹ√DER “adult male, man (of any race)” with strengthened variant ᴹ√NDER “bridegroom”, but with the Quenya root becoming ᴹ√NĒR “man” under the influence of ᴹ√NĪ “woman” (Ety/DER, NDER, NĒR, NĪ); from this point forward Noldorin/Sindarin derivatives began with d-, such as S./N. dîr “man”. However, in the first version of Tengwesta Qenderinwa from this same period, the primitive root is given as ᴹ√NER “man” (TQ1: PE18/35). On the other hand in Quendian & Common Eldarin Verbal Structure, also from the late 1930s, the root was given as ᴹ√(N)DER “man, male”, again as a strengthening of ᴹ√DER (EVS1: PE22/98).
Starting in the 1950s, Tolkien was more consistent in making the base root √NER with strengthened form √NDER. Tolkien gave √NDER/NER “male person” in Common Eldarin: Verb Structure (EVS2: PE22/133) and Common Eldarin: Noun Structure (PE21/70), both from the early 1950s. In the Quendi and Eldar essay from 1959-60 the base root was √NERE, though Tolkien clarified that the base root as referred more specifically to “physical strength and valour” (WJ/393). The root is given as √NER “man, male” in notes from the late 1960s (VT47/33).