"next in order after the nineteenth; an ordinal numeral; being one of twenty equal parts into which a whole is regarded as divided;" 16c., from twenty + -th (1), replacing Middle English twentithe, from Old English twentigoða. The Twentieth Century Limited was an express train from New York to Chicago 1902-1967.
late 14c., "to employ, put into active use," from exercise (n.); originally "to make use of;" also in regard to mental and spiritual training. The sense of "engage in physical activity" is from 1650s. Also from late 14c. in the sense of "train, drill, discipline, educate (someone); develop (a skill) by practice." Related: Exercised; exercises; exercising.
1889, "write program notes" (a sense now obsolete); 1896 as "arrange according to program," from program (n.).
Of computers, "cause to be automatically regulated in a prescribed way" from 1945; this was extended to animals by 1963 in the figurative sense of "to train to behave in a predetermined way;" of humans by 1966. Related: Programmed; programming.
A feature of all ancient Greek communities, at first it was merely an open space, later with extensive facilities and including training for the mind as well as the body. Hence its use in German from 15c. as a name for "high school" (more or less paralleling a sense also in Latin); in English it has remained purely athletic. For the "continental high school sense," English in 19c. sometimes used gymnastical as an adjective, gymnasiast for a student.