Meaning: A compliment that also insults or puts down at the same time.
Example: They gave me a backhanded compliment when they said I was smart for a girl.
Origin: Back-handed is synonymous with left-handed. For example in tennis, a backhand stroke is a strike by a right-handed player from the left side of the body. The left side of the body has always been deemed sinister. The Latin word for left is sinestra. Hence, back-handed means round-about, indirect, or devious.
Origin: "Break a leg" is sourced in superstition. It is a wish of good luck, but the words wish just the opposite.
It was once common for people to believe in Sprites. Sprites are actually spirits or ghosts that were believed to enjoy wreaking havoc and causing trouble. If the Sprites heard you ask for something, they were reputed to try to make the opposite happen.
Telling someone to "break a leg" is an attempt to outsmart the Sprites and in fact make something good happen. Sort of a medieval reverse psychology.
Of course it has became a popular wish of luck for theater performers.
Meaning: To be boasting without being able to back it up, talking about action without intent to follow through.
Example: Do you really want to buy this car or are you just blowing smoke?
Origin: Magicians often use smoke in their performance to obscure your view and conceal a bit of trickery. A person who is "blowing smoke" is tricking you and attempting to cover it up.
Meaning: To enjoy oneself by relaxing normal formalities.
Example: He is a true workaholic who has misguided priorities, when he wants to blow off some steam he comes to work on Saturday wearing blue jeans.
Origin: Boilers are commonly used in steam heating systems and steam engines such as those used in a steam locomotive. The boilers contain water that is heated by burning some fuel such as oil. The heated water turns to steam, which is then sent through a system of radiators (in the case of heating systems) or harnessed by a steam engine.
The steam creates considerable pressure in the boiler. If the pressure becomes too great, there is a danger of the boiler exploding. Hence boilers are equipped with safety valves called blow off valves that open if the pressure becomes to great.
"Blowing off steam" prevents explosions by relieving the pressure in a boiler by venting excess steam and pressure.
