conflagrate (v.)

1650s, "to catch fire," from Latin conflagratus, past participle of conflagrare "to burn, consume," 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." Transitive meaning "to set on fire" is from 1835.