exercise

English exercise comes from Middle English exercise, borrowed from Old French exercise, from Latin exercitium, a noun formed from the verb exerceō — itself ex- ('out') joined to arceō ('to enclose, keep in'), from Proto-Indo-European *h₂erk-.

The word arrived in English fully formed through French and Latin, with no recorded shift in sense along the way. Its most notable effect on English was pushing out the native Old English word plega ('an exercise'), which survives today as 'play'.

No other English cognate is given in the record, but its own history quietly explains 'play': plega was the word exercise replaced.