"Merde" is used in the same sense as "Break a leg" when one is dealing with dancers; when you would ordinarily (outside of the theatre and our insane superstitions) say "good luck," you'd instead say "merde" to wish dancers luck in their performance.
Holy Cadiddlehopper, Batman, you're kidding!
I use "break a leg" all the time, but have *never* heard "merde" used that way. Guess that shows how many dancing gigs I've done (or not!), eh?
I'm gobsmacked. Thanks for the education.
Ew. Don't know that I could ever use it...