A negative adjective appearing as {(a)láqa >>} alla in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/105 note #67), so probably meaning “✱no” as in alla Elda pole quete “no Elf can say”. It can also be used pronominally to mean “nothing”, and for this function it has a variant lála (PE23/104). For example: merin alla “I want nothing”, or merin alla sino “I want none of this”.
Qenya
(a)láqainen
adverb. by no means
alla
none, nothing, none, nothing, *no [adj.]
A correlative combination appearing as {láqainen >>} ᴹQ. (a)láqainen “by no means” in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/111), a combination of ᴹQ. láqa “none” and the instrumental suffix ᴹQ. -nen.
Neo-Quenya: For purposes of Neo-Quenya I would update this to ᴺQ. allanen “by no means” using later ᴹQ. alla “none”, also from DRC.