English idiom used in theatre to wish a performer "good luck"
"Break a leg" is a typical English idiom used in the context of theatre or other performing arts to wish a performer "good luck". An ironic or non-literal saying of uncertain origin (a dead metaphor), "break a leg" is commonly said to actors and musicians before they go on stage to perform, likely first used in this context in the United States in the 1930s or possibly 1920s, originally documented... Wikipedia