1. Cassie is as mad as a hatter, but she's my most interesting friend.
Meaning: crazy, strange, eccentric.
Origin: People who worked in felt-hat companies in the 1800s inhaled fumes of mercuric nitrate (which was used to stiffen the material) and, as a result, developed twitches, jumbled their speech, and grew confused. The condition was sometimes mistaken for madness and gave birth to the expression "mad as a hatter."
2. She made no bones about the fact that she disapproved of guests wearing shoes on her carpet.
Meaning: to speak directly, plainly, honestly, and without hesitation or doubt.
Origin: This was first used in print in 1548. It came about from the fact that if there are no bones in your soup, you can just swallow it without worrying about choking. That's like speaking plainly without worrying.
3. Make sure you mind your P's and Q's when the principal visits our classroom.
Meaning: to be extremely exact; be careful not to say or do anything wrong; mind your manners.
While the origins aren't entirely clear, it's been used these ways in the past:
1) This term was beginning to be used in the 1600s. In old English pubs, a list of the pints (P's) and quarts (Q's) a drinker consumed were written on a blackboard to be paid for later.
2) Pieds and queues are dance steps that a French dancing instructor would teach his students to perform with care.
4. Ford has to get this monkey off his back and lay off the dope.
Meaning: stop a bad habit (most often drug or drink addiction), be rid of something.
Origin: A monkey can be a cute, playful animal, but it can also be a clingy burden. Not many of us would want a wild, untrained monkey on our back (especially not Ashley N. who commented the other day about her dislike of monkeys). So someone who is struggling with a "monkey on their back" is struggling with an overwhelming or troubling burden.