ignis fatuus
‘a phosphorescent light that hovers or flits over swampy ground at night’
Lexical development traced from the Tamil root:
Lat. igneus ‘of fire, fiery; on fire; burning hot’ < ignis ‘fire, a fire’ + fatuous < igni < egni- < Tamil akkiṉi
ignis fatuus
English words derived from Tamil akkiṉi connoting 'heat'