exerciseyoudaoicibaDictYouDict[exercise 词源字典]
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[exercise etymology, exercise origin, 英语词源]
exercise (n.)youdaoicibaDictYouDict
mid-14c., "condition of being in active operation; practice for the sake of training," from Old French exercice (13c.) "exercise, execution of power; physical or spiritual exercise," from Latin exercitium "training, exercise" (of soldiers, horsemen, etc.); "play;" in Medieval Latin also of arts, from exercitare, frequentative of exercere "keep busy, keep at work, oversee, engage busily; train, exercise; practice, follow; carry into effect; disturb, disquiet," literally "remove restraint," from ex- "off" (see ex-) + arcere "keep away, prevent, enclose," from PIE *ark- "to hold, contain, guard" (see arcane).

Original sense may have been driving farm animals to the field to plow. Meaning "physical activity for fitness, etc." first recorded in English late 14c. Also from late 14c. as "a carrying out of an action; a doing or practicing; a disciplinary task." In reference to written schoolwork from early 17c. The ending was abstracted for formations such as dancercise (1967); jazzercise (1977); and boxercise (1985).
exercise (v.)youdaoicibaDictYouDict
late 14c., "to employ, put into active use," from exercise (n.); originally "to make use of;" also in regard to mental and spiritual training; sense of "engage in physical activity" is from 1650s. From late 14c. in sense of "train, drill, discipline, educate (someone); develop (a skill) by practice." Related: Exercised; exercises; exercising.