I agree, a lot of the idioms, make absolutely no sense in today's world!
However, when you trace them back, there is often a "sensible" rationale, from whence they came!
I have always thought this cats and dogs story was a good one ..... even making sense!
Found here, with lots more explanations.
https://www.google.ca/search?q=origi...hrome&ie=UTF-8
I find it a real stretch for cute as a button, but here you go ............
http://ndsmcobserver.com/2013/03/cute-as-a-button/
The origins of most of these "strange-to-us" sayings can usually be found
via a simple google of "origin plus the saying".