Archaic KJV Word
Study
Modern equivalent: make it your aim
What Was Lost
The passionate intentionality. 'Study to be quiet' did not mean read books about quietness but make it your passionate aim, your life's ambition, to live quietly. 'Study to shew thyself approved' meant eagerly, zealously pursue God's approval with everything you have. The academic meaning drained the urgency entirely.
Closest Survivor in Modern English
studious (retains some of the 'diligent/eager' sense alongside the academic meaning)
Peak Usage (1611)
KJV 1 Thessalonians 4:11 -- 'Study to be quiet'; 2 Timothy 2:15 -- 'Study to shew thyself approved unto God'
Died ~1800 (the 'be diligent/make it your aim' meaning faded)
Narrowed from 'to be diligent/to make it your earnest aim/to strive eagerly' (Latin studere 'to be eager/zealous') to only 'to read books for learning,' academicizing a word about passionate pursuit.
What Replaced It
“be diligent”
Work-focused; study-as-aim meant to set your whole desire on achieving something
“make every effort”
Compound and effortful; study was a single word for eager, passionate pursuit
“strive”
Implies struggle; study-as-aim was not about difficulty but about focused desire