A word appearing as ᴱQ. palo (palu-) in the Qenya Lexicon of the 1910s, glossed “plane surface, plain, the flat” and based on the early root ᴱ√PALA having to do with flat things (QL/71).

Neo-Quenya: Since √PAL continued to be used for wide and flat things in Tolkien’s later writing, I would retain ᴺQ. palo for purposes of Neo-Quenya. However, I would use it for abstractions like “plane (surface), the flat, *flatness” and not for a regional “plain” for which I would use later words like ᴹQ. landa or ᴹQ. palar. I would further assume that palo can be used for a flat plane in any direction, not just horizontal.