The Quenya word for “feather” and the name of tengwa #4 [z] (LotR/1122).
Conceptual Development: Some similar words appeared in the Qenya Lexicon of the 1910s under the early root ᴱ√QASA: ᴱQ. qasil “arrow-feather, arrow” and ᴱQ. qasilla “tuft, nodding spray, tassel, plume” (QL/76); quasil was only glossed “arrow” in the contemporaneous Poetic and Mythological Words of Eldarissa (PME/76). ᴹQ. qesse “feather” first appeared in The Etymologies of the 1930s under the root ᴹ√KWES (Ety/KWES), already the name of tengwa #4 (EtyAC/KWES). It was also the name of this tengwa in notes on the Feanorian Alphabet from the 1930s and 1940s (PE22/22, 51, 61), and remained so into the published version of The Lord of the Rings.
fëa noun "spirit" (pl. fëar attested, MR:363). The Incarnates are said to live by necessary union of hroa (body) and fëa (WJ:405). In Airëfëa noun "the Holy Spirit", Fëanáro masc. name "Spirit of Fire" (Quenya-Sindarin hybrid form: Fëanor), Fëanturi noun "Masters of Spirits", name of the two Valar Mandos and Lórien (SA:tur), fëafelmë noun "spirit-impulse" (impulses originating with the spirit, e.g. love, pity, anger, hate) (VT41:19 cf. 13, VT43:37). In one source it is said to mean specifically a "spirit indwelling a body", i.e. "soul" (PE17:124), which contradicts such uses as Airefëa or Fëanturi. Cf. fairë.