flame (n.) Look up flame at Dictionary.com
mid-14c., from Anglo-French flaume, Old French flamme (10c.), from Latin flammula "small flame," diminutive of flamma "flame, blazing fire," from PIE *bhleg- "to shine, flash," from root *bhel- (1) "to shine, flash, burn" (see bleach (v.)).

The meaning "a sweetheart" is attested from 1640s; the figurative sense of "burning passion" was in Middle English. Flame-thrower (1917) translates German flammenwerfer (1915).
flame (v.) Look up flame at Dictionary.com
early 14c., flamen, from Old French flamer, from flamme (see flame (n.)). The sense of "unleash invective on a computer network" is from 1980s. Related: Flamed; flaming.