ignite: [17] The Latin word for ‘fire’ was ignis (it has been traced back to a prehistoric Indo- European *egni- or *ogni-, which also produced Sanskrit agni- and Lithuanian ugnìs ‘fire’). From it were derived the verb ignīre ‘set light to’, source of English ignite, and the adjective igneus, from which English got igneous [17]. Another contribution the Latin noun has made to English is ignis fatuus ‘will-o’-the-wisp’ [16], literally ‘foolish fire’, so called perhaps from its erratic flickering, as if scatter-brained.
ignite (v.)
1660s, from Latin ignitus, past participle of ignire "set on fire," from ignis "fire" (see igneous). Attested earlier as an adjective (1550s). Related: Ignited; igniting.