come hell or high water

ever wonder where often-used phrases come from? i find myself saying something familiar then immediately wondering who coined that phrase and why. where did "coin a phrase" come from anyway?

mind your Ps and Qs (what's wrong with Bs and Cs?)
throw the baby out with the bath water (why not the old man?)
oh for God's sake (why bring him into this?)
a penny for your thoughts (i'd rather have a dollar)
fair to middlin (i get fair, but what the heck is middlin?)
what's shakin? (lots of things are shakin but why do you want to know that?)
how do you like them apples? (what apples?)
from soup to nuts (shouldn't that be from appetizer to dessert?)
johnny come lately (he can come late, but how does he come lately? and who's Johnny?)
one-trick pony (am i a pony? seriously)
fiddle sticks (no clue whatsoever)
let the cat out of the bag (someone keeps a cat in a bag? call the humane society!)
bring home the bacon (i'd rather bring home a paycheck than a pork product)
hit rock bottom (do we know there are rocks on the bottom? could be sand or grass)
what a sap (how did he turn into a gummy tree substance and why is it bad to do so?)
Jack of all trades (what if his name is Harry or Steve?)
Jumping Jack Flash (Jack gets around and he is very active)
another county heard from (what about the city or state? don't they have an opinion?)
it's raining cats and dogs (what? are there farm animals too?)
up at the crack of dawn (did it break?)

so many more, too many to think of. guess i'll just take a powder.