Mmmmm, very interesting post, santa.
![Wink [;)]](/emoticons/emotion-5.gif)
I knew about where f**k came from. But I didn't know about the origin of "Goodnight, sleep tight", which is a very funny expression for me.
How about these?
To be in another person's shoes -- to take someone's place. In the Viking age, when a man adopted a son, the boy accepted by putting on the man's shoes.
Done in cold blood -- done with no feeling. People believed your temper was ruled by the temperature of your blood. A hot-blooded person had a fierce temper, a cold-blooded person had no temper. So, if a cold-blooded person harmed you they did it in a calm, cruel and calculating manner.
Making both ends meet --having enough money to survive. This was a spelling mistake. In the 19th century business accounts were added up in columns. If the ends of both columns were equal then you had enough money - if they didn't then you were short of money. But the actual word used was
mete - an old word for equal.