Why "break a leg"?

Goodluck! Thank you, why not just use these polite word commonly know to people in all walks of life old and young, rich and poor. A more popular word is used to substitute this meaning of well wishes towards performing artist whether theater or musicians or even in sports play. "Break a leg". Do we really know what to tell our 10 year old daughter "break a leg" just before she goes to perform a dance or act in a musical infront of her school. These words are said to mean goodluck in these context when use, but we must very becareful in the sense that - the thing about history is  that we were not around when these words and other events happened. We are lead by often a third person viewer prospective or historians where messages could have been filtered down or even changed.

Regardless the word "break a leg" may just have been opposite of to the meaning we know today.

People in theatre consider it bad luck to wish an actor good luck, so instead they wish the opposite, by saying "break a leg!"

On October 1, 1921 in the New Statesman, a British liberal political and cultural magazine, an article was published, "A Defence of Superstition", written by urbane Irish nationalist Robert Wilson Lynd. Lynd said that the theatre was the second-most superstitious institution in England, after horse racing. In horse racing, Lynd asserted, to wish a man luck is considered unlucky, so "You should say something insulting such as, 'May you break your leg!'" Lynd did not attribute the phrase in any way to theatre people, though he was familiar with many of them.

So next time you tell somebody break a leg make sure is not someone you care about or just replace the 3 worded sentence with goodluck.