igneous (adj.) Look up igneous at Dictionary.com
1660s, "pertaining to or resembling fire," from Latin igneus "of fire, fiery; on fire; burning hot," figuratively "ardent, vehement," from ignis "fire, a fire," extended to "brightness, splendor, glow;" figuratively "rage, fury, passion," from PIE root *egni- "fire" (cognates: Sanskrit agnih "fire, sacrificial fire," Old Church Slavonic ogni, Lithuanian ugnis "fire"). Geological meaning "produced by volcanic forces" is from 1791, originally in distinction from aqueous. Earlier in the sense "fiery" were ignean (1630s), ignic (1610s).