The correlative combinations ᴹQ. {aláqe, lāqe >>} alle, allane “nobody, nothing, no one” appeared Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/103 and note #41), proniminal forms of ᴹQ. alla “none”. There was also an archaic variant form †lálane and a more elaborate form ᴹQ. láqane “nobody, at all”. Drafts has laqe “nobody” in the phrase ᴹQ. tasse ni·kenne laqe imma “there I saw nobody whatsoever” (PE23/101-102 note #36).
Neo-Quenya: For purposes of Neo-Quenya I would use ᴺQ. alquen for “nobody, no one”, inspired by Q. ilquen “everbody”. Other neologisms for “nobody” include ᴺQ. alaquen from the NQW and ᴺQ. úquen from ABNW (ABNW) from the early 2000s. For “nothing” I would just use ᴹQ. alla.
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”.