1814, from craunch (1630s), probably of imitative origin. Related: Crunched; crunching. The noun is 1836, from the verb; the sense of "critical moment" was popularized 1939 by Winston Churchill, who had used it in his 1938 biography of Marlborough.
To do arithmetic or mathematics; calculate: But if the general reader is up to crunching some numbers, Sportsbiz could be a pleasing ticket to understanding the money in sports (1980s+ Computer)
: : It's Crunch Time in the Havensnoun