In addition to being French for, "shit", "Merde" is a term used by ballet dancers (male or female) before they go on stage. This is the equivalent to "break a leg" in theatre.
france for 'shit'. Means 'good luck' in show business. Comes from long time ago, when a lot of people go to see a play, coach's horses shit all over the parking. They whishes 'shit' to wish lot of people in your play.