An earlier Quenya name for the Sun appearing in Silmarillion drafts from the 1930s and glossed “Fiery” (LR/240). It was sometimes used in combination with its other name Anar: Úr-anar “Red Sun” (LR/72). In a deleted entry in The Etymologies, it was given as a derivative of the root ᴹ√UR “be hot” (Ety/UR).
Qenya
úr
noun. fire, heat
úrin
proper name. Sun, (lit.) Fiery
en kárielto eldain isil, hildin úr-anar; toi írimar
for Elves they made the Moon, but for Men the red Sun; which are beautiful
anar
noun. Sun
yo
conjunction. and
anaróre
noun. sunrise
ye
conjunction. and
yu
conjunction. and
The word ᴹQ. úr “fire” appeared in The Etymologies of the 1930s under the root ᴹ√UR “be hot”, but this word was deleted when Tolkien revised the meaning of the root to “wide, large, great” (Ety/UR). However, the root √UR “heat” reappeared in later writings (PE22/160), and úr “fire” appeared in The Feanorian Alphabet of the 1930s as the name of tengwa #36 [.] (PE22/23). It reappeared again in the version of that document from the 1940s, but with the gloss “fire, heat” (PE22/51). In the 1st edition of The Lord of the Rings, the name of tengwa #36 was úr “heat” (RC/736), revised in the 2nd edition to Q. úrë “heat” (LotR/1123).
Conceptual Development: The earliest precursor of ᴹQ. úr “fire” was ᴱQ. uru “fire” from the Qenya Lexicon of the 1910s under the early root ᴱ√URU (QL/98).
Neo-Quenya: Based on the development of the names for tengwa #36, it seems 1930s úr “fire” >> 1940s úr “fire, heat” >> 1950s úr “heat” >> 1960s úre “heat”. However, the introduction of Q. úrë “heat” might mean that úr could once again be used for “fire”, and this has long been a popular word in Neo-Quenya. I would retain úr for that purpose, as it also allows us to salvage several fire-related related adjectives. It is possible, though, that the root √UR was restricted to “heat” and can no longer be used for “fire”.