Why do we "crunch numbers" when solving math problems — particularly in accounting and financial roles?

I heard someone say this today, and it dawned on me that I cannot see a clear source to it.

Does this go back to adding machines and other mechanical integrators? It seems plausible, but the term does not appear in print until around the mid 1970's.

update: Per @JHCL's comment: "number-grinding", and related forms, maybe very relevant to this topic — but they do not yet appear in Google ngrams. Great digging thus far...

Solution 1:

According to the The American Heritage Dictionary of Idioms, 2013:

crunch numbers: Perform numerous calculations or process a large amount of numerical data. For example, Preparing John’s presentation to the Federal Reserve Board required many hours of crunching numbers. This term originated with the computer age and indeed still applies mostly to the operations of computers. [Slang; second half of 1900s]

This could be related to the mechanical conception of punch cards for early computers, and the sound made by the machine while computing.

For instance, in Law Enforcement in the United States, James A. Conser, Gregory D. Russell, Terry E. Gingerich, Rebecca Paynich, Appendix 11-A, The evolution of information technology, one finds:

1943 : IBM and Howard Aiken succeeded in building the Mark I, a machine using punched paper tape that could "crunch" numbers up to 23 digits long.

A reference to crunching also appears on the above link to H. Aiken:

he saw how fields like mathematics and even sociology were hampered by their ability to crunch numbers—not unlike today’s push for taming Big Data.

In Makin' Numbers: Howard Aiken and the Computer, 1999, Cohen et al., one read that many cycles of operations could be running without visible mechanical motion,

however, even in this event the trained ear would know that the machine was still "crunching" numbers

Apparently, crunch came around 1795-1805 as a blend of craunch and crush.