Fourth great battle of the Wars of Beleriand, translated “Battle of Sudden Flame” (S/151), a combination of dagor “battle” and bragollach “sudden flame” (possibly = “wild fire”).
Conceptual Development: In Silmarillion drafts from the 1930s, this battle was first named N. Dagor Húr-Breged “Battle of Sudden Flame” (SM/317) or “Fire” (LR/132). This was revised to N. Dagor Vregedúr “Battle of Sudden Fire” (LR/280), a form that also appeared in The Etymologies where the second element was indicated to be the lenited form of N. bregedur “wild fire” (Ety/BERÉK). The name took on its final form in Silmarillion revisions from the 1950s-60s (WJ/52, 124).
dagor (“battle”), bragol (“sudden”) + lach (“flame”)