A word for “once” = “at one time (in the past)”, an adjectival form of né “ago” (VT49/31). It has two variants néya and nea. Compare also [ᴱQ.] ellume “once” = “one time”: á care sa ellume “do it once [one time only]” vs. carnes sa néya “he/she did it once [in the past]”. Very likely néya more strongly implies “pastness” than “oneness” and does not literally mean “only one time”, which could instead be expressed: carnes sa ellume.
Quenya
néya
néya
néya
adverb. once, at one time
nëa
once, at one time
nëa (1) "once, at one time" (in the past) (VT49:31). Also néya.
nëa
adverb. once, at one time
néya, see nëa #1