A verb for “to fade” indicated by the season and month names quellë “fading” and Narquelië “Sun-fading” in The Lord of the Rings appendices (LotR/1110). It was clearly derived from the root √KWEL “fade, die away, grow faint” (PE18/103).
Conceptual Development: This verb dates back to the Qenya Lexicon of the 1910s, where ᴱQ. qele- “perish, etc.” appeared under the early root ᴱ√QELE “perish, die, decay, fail” (QL/76). In Early Qenya Word-lists of the 1920s, qel- was glossed “fade” (PE16/134). In ᴹQ. Fíriel’s Song from the 1930s it appeared in its future form ᴹQ. qeluva “faileth” (LR/63, 72).
#quel- ("q")vb. "to fail" (wane, wither, fade; compare the nouns quelië "waning", quellë "fading"), only attested in the future tense (queluva in FS).