The word ñáva appeared in notes associated with the Quendi and Eldar essay from 1959-60, where it was the basis of several words having to do with consonants: Q. návear “consonants” and Q. ñáva-tengwi “consonants” as the tengwi that were “chiefly dependent on the movements in the mouth (including the lips)” (VT39/8). In drafts of this document, Tolkien instead had pávatengwi based on páva “mouth (including tongue, lips and teeth)” (VT39/19, notes #12 and #13), so presumably its replacement ñáva had a similar meaning.

In notes from around 1964 Tolkien instead had the root √KARAP for the “whole [mouth] apparatus for eating, drinking and speaking, including lips, teeth, cavity with palate and tongue”, along with an apparent noun form Q. karpa, though Tolkien indicated this word was actually used for a “phonetic system”. However, in this note he seemed to have revised {√KARAP >> √PATAK >>} √PAKAT, the last of which only had words for “speech” and not “speech apparatus”.

Neo-Quenya: Since √KARAP >> √PAKAT, for purposes of Neo-Quenya I’d retain ñava and give it the sense of páva for the entire mouth apparatus used for producing speech, and especially for producing consonants. It is likely a technical term, less commonly used than Q. anto “mouth”.