An adjective in The Etymologies of the 1930s glossed “dead (of mortals)” under the root ᴹ√PHIR “die of natural causes”, used as a plural noun in the name Dor Firn i Guinar “Land of the Dead that Live” (Ety/PHIR). Christopher Tolkien choose to include the name Dor Firn-i-Guinar in the published version of The Silmarillion (S/188), and most Sindarin writers accept its ongoing validity.
Noldorin
fern
noun/adjective. dead (of mortals)
fern
noun/adjective. dead (of mortals)
fern
noun/adjective. dead person
brethel
noun. beech, beech-tree, silver birch
brethel
noun. beech
brethil
noun. beech
fêr
noun. beech-tree
fêr
noun. beech-tree
A word for “beech-tree” in The Etymologies of the 1930s derived from the root ᴹ√PHER(EN) “beech” (Ety/PHER). Tolkien said that “Exilic fêr was usually replaced by brethil”, indicating that fêr was probably archaic. In The Etymologies, N. brethil was “beech-tree” (Ety/BERÉTH).
Neo-Sindarin: In Tolkien’s later writings, he typically said S. brethil was a type of silver-birch. I would assume the ordinary Sindarin word for “beech” was instead neldor (LotR/469; RC/384), but would keep †fêr as an archaic word for “beech”.