Archaic KJV Word
Deer
Modern equivalent: animal
What Was Lost
The native English word for 'animal' itself. When the Bible spoke of deer in the broadest sense, it meant all wild creatures -- the entire animal kingdom God created. The narrowing to one antlered species meant English lost its native, Germanic word for the whole animal world.
Closest Survivor in Modern English
German Tier ('animal' -- the cognate that kept the original breadth)
Peak Usage (1611)
KJV Deuteronomy 14:5 -- 'The hart, and the roebuck, and the fallow deer'; broader 1611 usage where 'deer' meant any wild animal
Died ~1700
Narrowed from 'any wild animal' (Old English deor, cognate with German Tier 'animal') to only the cervid family, shrinking a kingdom to a single genus.
What Replaced It
“animal”
Latin import that replaced the native Germanic word for all creatures
“beast”
Carried wildness but lacked the neutrality of the original deor
“wildlife”
Modern compound; deer-as-animal required no compound, it was the default word for any wild creature