Middle Primitive Elvish
boron-
verb. boron-
bor(on)
root. endure
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
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”.