1550s, "a destructive fire;" 1650s, "a large fire, the burning of a large mass of combustibles," from Middle French conflagration (16c.) or directly from Latin conflagrationem (nominative conflagratio), noun of action from pas-participle stem of conflagrare "to burn up," from assimilated form of com-, here probably an intensive prefix (see con-), + flagrare "to burn, blaze, glow," from PIE root *bhel- (1) "to shine, flash, burn."
