Q. súlë (súli-) [þ] n. “spirit, emission of power (of will or desire); breath”
A word for “spirit” appearing in The Lord of the Rings appendices, where it was given as the name of tengwa #9 [“s” from older “th”] (LotR/1123). It also meant “breath” (PE17/124) and was originally derived from the primitive root √THŪ “puff, blow” (PE17/124, Ety/THŪ), and thus indirectly related to súrë “wind”. In this respect, súlë resembled the Ancient Greek word πνεῦμα (“pneuma”), which also originally meant “breath” but came to be used for the spirit or soul.
Eldar did not confound ordinary “breath” of the lungs with “spirit” ... the Eldar held that “spirits”, the more as they had native power, could emit their influence to make contact with or act upon things exterior to themselves: primarily on upon other spirits, or other incarnate persons (via the fëar), but also in the case of great spirits (such as the Valar or greater Maiar) directly upon physical things without the mediacy of bodies normally necessary in the case of fairondi or incarnates. To describe this, they used (but by deliberate symbolism taken e.g. from such cases as their breathing upon a cold or frosted surface, which was then melted) the √THŪ [“breath”] ... Hence [primitive Eldarin] thū́lē “blowing forth” was used = “spirit” in this special sense: the emission of power (of will or desire) from a spirit. (PE17/124)
Thus súlë was used metaphorically as “spirit” in the sense of the expression of a spirit’s power or will upon the world, along side its more ordinary meaning as “breath”.
Conceptual Development: This word first appeared in the Etymologies from the 1930s, already with the meaning and etymology given above (Ety/THŪ).
References ✧ LotR/1123; PE17/124
ᴹQ. súle (súli-) [þ] n. “breath; spirit”
References ✧ Ety/THŪ; PE22/50, 119