A word for “fire” attested in later writings only as an element in names, such as S. Úrui “August, ✱Hot-one” (LotR/1110). It appeared as N. ûr “fire” in The Etymologies of the 1930s under the root ᴹ√UR “be hot”, but this and related words were deleted when Tolkien changed the sense of the root to “wide, large, great” (Ety/UR). However, √UR “heat” was restored in later writings (PE17/148; PE22/160), and primitive ✶ūr “a fire (on hearth)” appeared in Common Eldarin: Noun Structure from the early 1950s, though Tolkien did mark it with a “?” (PE21/71 and note #8).
Conceptual Development: Perhaps the first precursor to this word was G. †Uril, an archaic word for the Sun in the Gnomish Lexicon of the 1910s appearing beside its modern form G. Aur (GL/75) and clearly a derivative of the early root ᴱ√URU as suggested by Christopher Tolkien (LT1A/Ûr; QL/098). In Gnomish Lexicon Slips revising this document, it became {ŷr >>} hŷr “sun” (PE13/114), and in Early Noldorin Word-lists of the 1920s it became ᴱN. {húr >>} úr “sun”, derived from primitive ᴱ✶ourū̆ (PE13/155).
This in turn became N. ûr “fire” in The Etymologies of the 1930s under ᴹ√UR “be hot”, but as noted above the meaning of this root was changed in that document (Ety/UR). Although the root √UR “heat” was later restored, it isn’t clear whether Tolkien also restored ûr “fire”, though there is some secondary evidence of it: primitive ✶ūr “a fire (on hearth)” appeared in notes from the early 1950s, as also noted above (PE21/71).
Neo-Sindarin: If S. naur is (like its Quenya cognate Q. nár) more representative of an elemental or abstract notion of fire, then ûr might be used for an individual physical fire such as one in a fireplace.
Birth name of Lalaith (UT/57), perhaps a combination of ûr “fire” and the suffixal form -wen of gwend “maiden”.