Meaning of "sixty" in "The rain was coming down like sixty now."?

Solution 1:

It appears to mean with great force and speed.

After a search in the Corpus, I can't confidently say it simply means "very fast," taking 60 as the "breakneck driving speed" of sixty miles per hour. Although the exact origin is murky, it seems to be an inflated version of the earlier phrase "like forty," which reportedly enjoyed currency in the 17th century. The number forty has traditionally been used to refer to an indefinitely large number (with numerous examples in old fairy tales as well as the scripture), and it's not implausible for people to have ended a remark with "... like forty!" as an intensifier.

On the other hand, We know that at some point, people stopped saying forty in favor of the new number 60, using it to refer to things happening both forcefully and quickly ‒ perhaps imagining the force and the speed of a steam locomotive going full throttle! People wanted to sound hip and started to say "... like 60!" instead of the old and hackneyed "... like forty!"

Sampled from the corpus::

Burrcliff: Its Sunshine and Its Clouds (1854):

"...and the rain was streakin' it in there so like sixty."

The California Teacher - Volume 4 - Page 281 (1867):

"Ever since I sent Charlie to the public school he lies like sixty."