Archaic KJV Word
Quick
Modern equivalent: living
What Was Lost
The charged boundary between life and death. 'The quick and the dead' was not about speed and death but about the living and the dead standing before judgment. 'The word of God is quick' meant scripture itself is alive -- a living, breathing entity, not a fast one.
Closest Survivor in Modern English
quicksilver (mercury -- 'living silver' that moves as if alive)
Peak Usage (1611)
KJV Acts 10:42 -- 'Judge of quick and dead'; Hebrews 4:12 -- 'the word of God is quick, and powerful'
Died ~1850
Narrowed from 'living/alive' (Old English cwic) to 'fast/speedy,' collapsing a life-and-death distinction into a description of speed.
What Replaced It
“living”
Flat and ordinary; 'quick' as 'alive' carried urgency and vitality -- not merely existing but vibrantly alive
“alive”
Binary state word; quick implied animated, active, pulsing with life