conflagrate (v.)

1650s, "to catch fire," from Latin conflagratus, past participle of conflagrare "to burn, consume," from assimilated form of com-, here perhaps 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.