exercise: [14] The notion underlying exercise is of ‘removal of restraint’. It comes ultimately from Latin exercēre, a compound verb formed from the prefix ex- ‘out of, from’ and arcēre ‘restrain, enclose’ (source of English arcane and related to English ark). It has been speculated that this originally denoted the driving of draught animals out into the fields to plough, but however that may be, it soon developed the general senses ‘set to work, keep at work’ and ‘drill, practise’ which form the semantic basis of English exercise. => arcane, ark
