energy

English energy comes from Middle French énergie, from Late Latin energia, from Ancient Greek ἐνέργεια (enérgeia, "activity"). That Greek noun grew from ἐνεργός (energós, "active"), a fusion of ἐν (en, "in") and ἔργον (érgon, "work").

For centuries the word simply meant vigor or activity in a general sense. It gained its modern scientific meaning in 1802, when the English polymath Thomas Young used it in his lectures on Natural Philosophy to name a precise physical quantity.

The érgon at its core, meaning 'work,' is the same root that ties energy to the idea of labor built right into the word.