what these sayings really mean or where they came from?

Have you ever heard someone they were going to "wet their whistle"? You usually think their having a drink, usually of alcohol. The saying originated from pubs, when the ceramic cups would have whistles baked into them for the drinker to blow into to get a refill. 

When someone says they were "saved by the bell," they usually mean they were saved from doing something in the Nick of time by a distraction of some sort. But it came from the fear of being buried alive. Back in colonial and older times, a lot of people would be buried alive. To stop this happening so frequently, they would tie a string to the person's(the one who was being buried) hand, and tie the other end of the string to a bell which was tied to a tree branch. If the person buried would revive enough to ring the bell, the keepers would rush out and dig them up.

Getting a square meal now means getting a healthy meal, but in the colonial times, it was your dinner plate. You would carry a square piece of wood with a dip carved out to hold your serving of stew or whatever was being served. You would always carry your "square" when you traveled.

"Sleep tight, don't let the bed bugs bite" is a common saying in households with kids. But this saying is very literal. To "sleep tight" would mean to tighten ropes on old straw mattresses placed on bed frames. "Don't let the bed bugs bite" simply means don't let bedbugs bite!

http://www.goodwords.com/sayings/

When you butter someone up, you compliment them, usually because you want something from them. It came from an ancient Indian custom in which they would throw balls of clarified butter at statues of the gods/goddesses to seek their favor.



http://cheezburger.com/template/4884438



When your at home after a long day of working, you just want to let your hair down, or relax. This used to be literally done. Parisian nobles would be judged by their friends if they were in public without an elaborate hairdo. These hairstyles would take hours to create. So when they would go home, they would let their hair down and relax

 When you give someone the cold shoulder, you practically shun them, but in medieval times, giving someone the cold shoulder used to be a polite way to let a guest know it was time for them to leave. The host would wrap up a piece of cold meat(usually the shoulder) of beef, pork, or mutton(sheep).

http://list25.com/25-common-sayings-and-where-they-came-from/