mid-15c., "protraction, delay," verbal noun from train (v.). From 1540s as "discipline and instruction to develop powers or skills;" 1786 as "exercise to improve bodily vigor." Training wheels as an attachment to a bicycle is from 1953.
Training is the development of the mind or character or both, or some faculty, at some length, by exercise, as a soldier is trained or drilled. Discipline is essentially the same as training, but more severe. [Century Dictionary]
early 15c., impetous "rapid movement, rush;" 1640s, with modern spelling, "force with which a body moves, driving force," from Latin impetus "an attack, assault; rapid motion; an impulse; violence, vigor, force;" figuratively "ardor, passion," from impetere "to attack," from assimilated form of in- "into, in, on, upon" (from PIE root *en "in") + petere "aim for, rush at" (from PIE root *pet- "to rush, to fly").
late 15c., "recovery or regaining of things, recovery as of something lost" (a sense now obsolete), from Latin recuperationem (nominative recuperatio) "a getting back, regaining, recovery," noun of action from past-participle stem of recuperare "get back, regain, get again," in Medieval Latin "revive, convalesce, recover," which is related to or a variant of recipere "to hold, contain" (see receive). Meaning "restoration to health or vigor" is from 1865.
1680s, "sexual climax, the acme of venereal excitement," from French orgasme or Modern Latin orgasmus, from Greek orgasmos "excitement, swelling," from organ "be in heat, become ripe for," literally "to swell, be excited," related to orge "impulse, excitement, anger," from PIE root *wrog- "to burgeon, swell with strength" (source also of Sanskrit urja "a nourishment, sap, vigor," Old Irish ferc, ferg "anger"). Also used 17c. of other violent excitements of emotion or other bodily functions; broader sense of "immoderate excitement or action" is from 1763.
The second element is obscure. Watkins suggests a suffixed form of the PIE root *weie- "to go after something, pursue with vigor" (see gain (v.)); de Vaan also traces it to a PIE form meaning "pursued." Meaning "the spoken or written form in which a person is invited" is from 1610s.
1530s, "to suckle (an infant), nourish at the breast;" 1520s in the passive sense, "to bring up" (a child); alteration of Middle English nurshen, norishen "to supply with food and drink, feed; bring up, nurture" (c. 1300; see nourish), in part by influence of nurse (n.1). From 1540s as "promote growth or vigor in, encourage." Sense of "tend to in sickness or infirmity" is recorded by 1736. Related: Nursed; nursing.
From late 14c. as "lightheartedness, cheerfulness." A word with more senses in Middle and early Modern English than recently: "sexual pleasure or indulgence, lust" (mid-14c.); "insolent presumptuousness, impudence" (mid-14c.); "vigor, strength" (mid-14c.); "love; a love affair" (c. 1300, hence in jollity "by fornication, out of wedlock"); "gallantry" (1530s); "state of splendor" (1540s).
Old English piþa "central cylinder of the stems of plants," also, figuratively, "essential part, quintessence, condensed substance," from West Germanic *pithan- (source also of Middle Dutch pitte, Dutch pit, East Frisian pit), a Low German root of uncertain origin. Figurative sense of "energy, concentrated force, closeness and vigor of thought and style" is by 1520s. The pith helmet (1889, earlier pith hat, 1884) was so called because it is made from the dried pith of the Bengal spongewood.