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.
1837, from French Roi Charmant, name of the hero of Comtesse d'Aulnoy's "L'Oiseau Bleu" (1697). In English he was adopted into native fairy tales, such as "Sleeping Beauty" and "Cinderella."
As for me, I have always agreed with the fairy books that the moment when Prince Charming arrives is the perfect climax. Everything that goes before in the life of a girl simply leads up to that moment, and everything that comes after dates from it; and while the girl of the twentieth century, sallying forth in search of adventure, may not hope to meet at the next turn a knight in shining armor, or a sighing troubadour, she does hope, if she is normal and has the normal dreams of a girl, to find her hero in some of the men who pass her way. [Temple Bailey, "Adventures in Girlhood," Philadelphia, 1919]
"to have actual being of any kind, actually be at a certain moment or throughout a certain period of time," c. 1600, from French exister (17c.), from Latin existere/exsistere "to step out, stand forth, emerge, appear; exist, be" (see existence). "The late appearance of the word is remarkable" [OED]. Middle English often used ibēn, ibeon (based on be) for "to exist." Related: Existed; existing.
1860, a colloquial shortening of photograph. The verb is by 1865, from the noun. Photo-finish, of a race that ends with two or more competitors crossing the finishing line at nearly the same time (so a photograph taken at the finish line at the moment of crossing is the only way to determine who won) is attested from 1936. Photo opportunity "arranged opportunity to take a photograph of a notable person or event" is from 1974, said to be a coinage of the Nixon Administration.
"notch, groove, slit," mid-15c., nik, nyke, a word of unknown origin, possibly from a variant of Old French niche (see niche). Nick of time is first attested 1640s (nick of opportunity is 1610s), possibly from an old custom of recording time as it passed by making notches on a tally stick, though nick in the general sense of "critical moment" is older (1570s, Hanmer, who adds "as commonly we say") than the phrase. Nick (n.) specifically as "notch of a tally" is attested from late 15c.
"melody for a single voice," 1775, from Italian aria, literally "air" (see air (n.1)).
Historically considered, the aria marks a single moment in the course of a dramatic action. The text often consists of but a few words, many times repeated (as we find in Handel's oratorios, etc.), and the musical development is the main thing. The opposite of aria is recitative (q.v.), in which the declamation of the syllables is the main thing, colored, perhaps, by means of clever orchestration. [W.S.B. Mathews and Emil Liebling, "Dictionary of Music," 1896]