Archaic KJV Word
Power
Modern equivalent: political authority
What Was Lost
The supernatural capability. 'Ye shall receive dynamis' was not 'you will gain political authority' but 'you will receive supernatural capability to do what no human can do on their own.' The gospel as 'the power of God' meant it was not an idea but a force -- the active, transformative, death-defeating energy of God unleashed.
Closest Survivor in Modern English
dynamite (from dynamis -- Nobel named his explosive after the Greek word for divine power)
Peak Usage (1611)
KJV Acts 1:8 -- 'Ye shall receive power, after that the Holy Ghost is come upon you'; Romans 1:16 -- 'The gospel...is the power of God'
Died still used but politicized (~1800)
Greek dynamis ('inherent capability/miraculous force/the ability to do what is impossible by natural means') was politicized into 'authority over others.' Power became domination rather than divine capability.
What Replaced It
“authority”
Positional; dynamis was inherent capability -- the power that raised Christ from the dead
“control”
Domination; dynamis was enabling force, not controlling force
“influence”
Social capital; dynamis was supernatural ability to do the humanly impossible