late 15c., "act of annulling" (an ordinance, judgment, etc.), also "fact of being reversed," from reverse (v.) + -al (2).

"utopia," from title of a book published 1872 by British author Samuel Butler, a partial reversal of nowhere.

spelled-out form of K.O. (for knockout in the pugilism sense), from 1923. Also used in 1920s as a slang reversal of OK.

a reversal of opinion, 1819, French (17c.), from Italian volta faccia, literally "turn face," from volta, imperative of voltare "to turn" (from Vulgar Latin *volvita, from Latin volvere "to roll," from PIE root *wel- (3) "to turn, revolve") + faccia (see face).

also comeupance, "one's deserts, reversal or punishment that one deserves," 1859, presumably it is rooted in the same notion in the verbal phrase come up "present oneself for judgment before a tribunal" (see come + up (adv.)) + -ance.

also set-back, 1670s, "reversal, check to progress," from the verbal phrase, attested mid-15c. as "withhold;" see set (v.) + back (adv.). Backset (1721) is used in the same sense. The meaning "space between a building and a property line or roadway" is from 1916. To set (someone) back "cost" (a certain sum of money) is from 1900.

early 15c., "rejected as worthless," from Late Latin reprobatus, past participle of reprobare "disapprove, reject, condemn," from Latin re- "back, again," here perhaps indicating "opposite of, reversal of previous condition" (see re-) + probare "prove to be worthy" (see probate (n.)). The meaning "abandoned in character, morally depraved, unprincipled" is by 1650s.

c. 1300, repreven, repruve, reproeven, "accuse, charge as a fault," from Old French reprover "accuse, blame" (12c.), from Late Latin reprobare "disapprove, reject, condemn," from Latin re- "opposite of, reversal of previous condition" (see re-) + probare "prove to be worthy" (see probate (n.)).

From mid-14c. as "deliver a rebuke, admonish;" late 14c. as "disapprove, condemn, find fault with." Related: Reproved; reproving; reprovable.

1530s, "reversal of what is expected" (especially a fatal turning point in a drama, the winding up of the plot), from Latin catastropha, from Greek katastrophē "an overturning; a sudden end," from katastrephein "to overturn, turn down, trample on; to come to an end," from kata "down" (see cata-) + strephein "turn" (from PIE root *streb(h)- "to wind, turn"). The extension to "sudden disaster" is attested from 1748.

late 14c., reversioun, a legal word used in reference to the return of an estate to the heirs of a grantor on the expiration of the grant, from Old French reversion and directly from Latin reversionem (nominative reversio) "act of turning back," noun of action from past-participle stem of revertere (see revert). From early 15c. as "a return to a place."

reversion has various senses, chiefly legal or biological .... It suffices to say that they all correspond to the verb revert, & not to the verb reverse, whose noun is reversal. [Fowler]