Greek 'energeia' (actuality), coined by Aristotle — 'en-' + 'ergon' (work). Repurposed as a physics term in 1807.
The strength and vitality required for sustained physical or mental activity; in physics, the capacity of a system to do work.
From Late Latin 'energīa,' from Greek 'enérgeia' (ἐνέργεια, activity, operation, force), from 'energós' (ἐνεργός, active, at work), from 'en-' (in, at) + 'érgon' (work, deed), from PIE *werǵ- (to do, to work). Aristotle coined the philosophical sense of 'enérgeia' to mean 'actuality' — the realization of potential, as opposed to mere possibility ('dýnamis'). The physics term was introduced by Thomas Young in 1807, drawing
Aristotle invented the word 'enérgeia' as a philosophical term meaning 'actuality' — the state of being fully realized, as opposed to 'dýnamis' (potentiality). When Thomas Young repurposed it for physics in 1807, he was closer to Aristotle than he perhaps knew: kinetic energy is literally potential made actual, dýnamis becoming enérgeia.