The root ᴹ√BOR “endure” along with its extended form ᴹ√BORON appeared in The Etymologies of the 1930s along with various derivatives having to do with endurance, faithfulness and everlastingness (Ety/BOR, BORÓN). It was simply a later version of the root ᴱ√VORO from the Qenya Lexicon of the 1910s, unglossed but clearly of a similar meaning based on its Qenya and Gnomish derivatives like ᴱQ. voronda “faithful”, ᴱQ. vorima “everlasting” and G. bron(n) “steadfast, firm” (QL/102; GL/23-24).
Similar forms like Q. voronda or vórima “faithful” continued to appear in Tolkien’s later writing (UT/317). The well established names Q. Voronwë or S. Bronwe(g) “Steadfast, Faithful” retained the same basic form and meaning throughout Tolkien’s life, testifying to the enduring nature of the Elvish root for “endurance”.
An unglossed root in The Etymologies of the 1930s with derivatives like ᴹQ. uile “long trailing plant, especially seaweed” and N. uil “seaweed” (Ety/UY). In this document it also was the basis of the name of the Vali ᴹQ. Uinen, but in later writings Tolkien said this name was not Elvish, but was adapted from Valarin (WJ/404). This may mean the root ᴹ√UY was abandoned, but I would retain it for purposes of Neo-Eldarin to preserve these 1930s words for “seaweed”.