Thanks Helen for starting this book. Idioms are in many ways, really crazy. But fun to learn their origins.

One that I’ve never understood is the expression, ‘Break a leg’ which means ‘Good luck!!’ Huh?

This is what I found out about it.... 

Some say the term originated during Elizabethan times when, instead of applause, the audience would bang their chairs on the ground — and if they liked it enough, the leg of the chair would break. Where ‘good luck’ comes into it, I’m not sure.

There is another similar one, 'Shake a leg' meaning to, 'get a move on!' Now that one I can understand.

Another fun one, (if you can call it fun) is: Kick the bucket! How did that have anything to do with dying? 

This is what I learned....
Kick the bucket surfaced in print only at the end of the eighteenth century, and a legend spread “in the slang fraternity” almost at once that a certain person “who, having hung himself to a beam while standing on the bottom of an upturned pail, or bucket, kicked the vessel away and of course, died! 

Some seem obvious, like: You can’t make an omelet without breaking some eggs. 

But there is another meaning....

It is impossible to get something important done without creating a problem for someone else. So, the result may be good for you, but not for everyone. 
It originated in 1700 in the French language by François de Charette, and was translated into English in 1796. 

These idioms are a lot of fun and very interesting when you go into them. These are just three of the hundreds, possibly thousands, that are out there.