Archaic KJV Word
Wheat
Modern equivalent: grain commodity
What Was Lost
The death that produces life. 'Unless a grain of wheat falls into the ground and dies, it remains alone; but if it dies, it produces much grain.' Jesus used wheat to describe His own death -- the seed must die to produce the harvest. This was not agricultural advice but a theology of sacrificial death producing abundant life.
Closest Survivor in Modern English
wheat (still used in parables but the life-or-death, survival dependence is lost to grocery abundance)
Peak Usage (1611)
KJV Matthew 13:25 -- 'His enemy came and sowed tares among the wheat'; John 12:24 -- 'Except a corn of wheat fall into the ground and die'
Died still used but commodity-ized (~1800)
Hebrew chittah and Greek sitos ('wheat/the grain of life/the crop that meant survival or starvation') commoditized from life-and-death staple into a traded commodity. The existential dependence on the harvest was lost to industrial agriculture.
What Replaced It
“grain”
Agricultural commodity; wheat was the substance of daily survival -- no wheat meant death
“crop”
Farm product; wheat was the symbol of faithful people who endure until harvest
“cereal”
Breakfast food; a grain of wheat dying and bearing fruit was Christ's description of His own death