What is the origin of the idiom "break a leg" and when to use it?

The origin of the idiom "break a leg" is rooted in superstition within the world of theater. Actors traditionally believed that wishing someone good luck directly, such as saying "good luck," would bring about bad luck. To counteract such jinx, they adopted the practice of using the opposite phrase "break a leg" to wish each other success.The expression has become a well-known way to offer good luck and encouragement to performers, particularly before a theatrical or musical performance. Over time, it has extended to other areas of life where success is desired.