A noun appearing as N. {bregedúr >>} bregedur “wild fire” in The Etymologies of the 1930s, a combination of N. breged “suddenness” and N. ûr “fire”, from ᴹ√BEREK and ᴹ√UR “be hot” respectively (Ety/BERÉK, UR; EtyAC/MERÉK). It was also an element in the name N. Dagor Vregedúr “Battle of Sudden Fire” (Ety/BERÉK; LR/280) which in later writings became S. Dagor Bragollach “Battle of Sudden Flame” (S/151; WJ/52).

Neo-Sindarin: Despite this name change, I think bregedur “wild fire” might still be valid, given other late names like S. Bregalad “Quickbeam” and the continued use of the root √UR. In fact, I prefer this over using bragollach “sudden flame”, since bragol “sudden” has no other similar forms on Tolkien’s writings: it is breg- everywhere else.