"movable mechanical coupling or locking and unlocking contrivance for transmitting motion," 1814, from clutch (v.), with the "seizing" sense extended to "device for bringing working parts together." Originally of mill-works, first used of motor vehicles 1899. Meaning "moment when heroics are required" is attested from 1920s.
1520s, "attention, heedfulness; intention, purpose," from mindful + -ness. As "psychological process of bringing one's attention to experiences in the present moment," as developed through meditation, etc., it was in use by 1995; the word was used since late 19c. in translations of Buddhist texts (for sati).
plural of crossroad (q.v.). By 1795 in the figurative sense of "a turning point, a moment of decision;" earlier than the literal sense "point where two roads intersect." Formerly the prescribed burial place for suicides. In U.S., used for "a crossroads and little more; small, dull town" by 1845.
early 15c. classical correction of Middle English parfit "flawless, ideal" (c. 1300), also "complete, full, finished, lacking in no way" (late 14c.), from Old French parfit "finished, completed, ready" (11c.), from Latin perfectus "completed, excellent, accomplished, exquisite," past participle of perficere "accomplish, finish, complete," from per "completely" (see per) + combining form of facere "to make, to do" (from PIE root *dhe- "to set, put").
Often used in English as an intensive (perfect stranger, etc.), from the notion of "complete." Grammatical sense, in reference to verb tense describing an action as completed, is from c. 1500. As a noun, late 14c. ("perfection"), from the adjective.
The difference between the Preterit and the Perfect is in English observed more strictly than in the other languages possessing corresponding tenses. The Preterit refers to some time in the past without telling anything about the connexion with the present moment, while the Perfect is a retrospective present, which connects a past occurrence with the present time, either as continued up to the present moment (inclusive time) or as having results or consequences bearing on the present moment. [Otto Jespersen, "Essentials of English Grammar," 1933]
1814, "crush with the teeth," a variant of craunch (1630s), which probably is of imitative origin. Meaning "act or proceed with a sound of crunching" is by 1849. Related: Crunched; crunching.
The noun is 1836, "an act of crunching," from the verb; the sense of "critical moment" was popularized 1939 by Winston Churchill, who had used it in his 1938 biography of Marlborough.