Archaic KJV Word
Creature
Modern equivalent: creation
What Was Lost
The Creator-creature relationship. Every creature was defined by having been created -- the word itself was a permanent reminder of dependence on God. 'If any man be in Christ, he is a new creature' meant a new creation-act had occurred: God created again. When creature narrowed to 'animal,' the theological architecture of creation/Creator was weakened.
Closest Survivor in Modern English
creature (in 'new creature in Christ' -- theological usage preserves the broader meaning)
Peak Usage (1611)
KJV 2 Corinthians 5:17 -- 'If any man be in Christ, he is a new creature'; Romans 8:19 -- 'The earnest expectation of the creature'
Died still used but narrowed (~1900)
Narrowed from 'anything created/all of creation/a created being' (Latin creatura 'a thing created') to primarily 'an animal, especially a strange or repulsive one,' diminishing a word that once held all creation.
What Replaced It
“creation”
Abstract; creature-as-created-thing was personal and individual -- each creature was a specific act of God's creating
“being”
Philosophical; creature was theological -- defined by its relationship to the Creator
“animal”
The modern default association; creature meant any created thing, including humans