Archaic KJV Word
Fire
Modern equivalent: combustion
What Was Lost
The divine presence. Fire was not a metaphor for God -- it was the medium God chose to appear: burning bush, pillar of fire, Sinai in flames, tongues of fire at Pentecost. 'Our God is a consuming fire' was not metaphorical but experiential. To encounter God was to encounter fire -- purifying, illuminating, and dangerous.
Closest Survivor in Modern English
fire (still used metaphorically but the theophanic dimension is lost)
Peak Usage (1611)
KJV Exodus 3:2 -- 'The bush burned with fire, and the bush was not consumed'; Hebrews 12:29 -- 'Our God is a consuming fire'
Died still used but reduced (~1700)
Hebrew esh ('fire') was a primary theophany -- the medium of God's visible presence. It reduced to combustion chemistry, severing fire from its identity as the visible form God chose to manifest Himself.
What Replaced It
“combustion”
Chemical reaction; esh was the visible face of God's presence
“flames”
Physical phenomenon; the burning bush was not combustion but theophany -- God appearing
“destruction”
Negative only; biblical fire both destroyed (Sodom) and purified (refiner's fire) and was God's own presence (burning bush, Pentecost)