spin(id)

root. fine thread, filament; hair

Tolkien had Elvish “hair” words that began with fin- for most of his life, but the details of their derivation evolved. The earliest form of this root was unglossed ᴱ√FIÐI [FIÐI] in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. findl “lock of hair” and ᴱQ. firin “ray of sun” (QL/38). It also had derivatives in the contemporaneous Gnomish Lexicon such as G. fiðra “collective hair” and {findel >>} G. finn “a lock of hair” (GL/35), the latter an element in the name G. Glorfindel “Golden Hair”, a name that retained this form and meaning for all of Tolkien’s life.

In The Etymologies of the 1930s Tolkien had unglossed ᴹ√SPIN with derivatives like ᴹQ. finde “tress, braid of hair” and N. finnel “(braided) hair” (Ety/SPIN). He made a point that this root was distinct from ᴹ√PHIN “nimbleness, skill” (Ety/PHIN), a distinction he reemphasized in later writings as well (PE17/17, 119). The additional form ᴹQ. fine “larch” (a species of tree with needle-like leaves) indicates the 1930s root was not limited exclusively to “hair” (Ety/SPIN). The root √SPIN appeared a number of times in Tolkien’s later writings, variously glossed “single hair, filament” >> “fine thread, filament” (PE17/17), “lock, tress of human/elvish hair” as extended √SPIN-ID (PE17/119), or “single hair” (PE17/185). However, in The Shibboleth of Feanor from 1968 Tolkien gave the root as √PHIN “hair” (PM/340).

Neo-Eldarin: For purposes of Neo-Eldarin, I would ignore this 1968 change of √SPIN >> √PHIN. Furthermore, I would assume √SPIN referred to a single hair or other kind of filament, and extended √SPINID referred to a tress of hair.