A word appearing as {phende >>} fende “door” in Late Notes on Verb Structure (LVS) from 1969 (PE22/166 and note #112). The deleted variant probably indicates its primitive form.
Conceptual Development: The earliest “door” word was ᴱQ. posta in the Qenya Lexicon of the 1910s under the early root {ᴱ√PONO >>} ᴱ√BOÐO (QL/75). Another precursor was ᴹQ. fenda “threshold” in The Etymologies of the 1930s under the root ᴹ√PHEN (Ety/PHEN). In notes from December 1959 (D59) Tolkien gave Q. fenna as a derivative of √PHEN and cognate to S. fen, all meaning “door” (PE17/181).
Neo-Quenya: For purposes of Neo-Quenya, I prefer 1969 fendë as the word for “door”, but I think [ᴹQ.] fenda “threshold” might remain viable as a separate derivative of the root.
fenna noun "door" (PE17:45, 181)