It is a strange thing to say when you mean ‘good luck’, so why do we say it?
There are all kinds of theories. Our favourite and probably the most logical is based in days of Music Hall and Vaudeville (late 1800’s – early 1900’s). The managing company would often book more acts than could be accommodated in an evening’s entertainment, but would only pay those that actually got on stage.
As we explain to our students every year at the SandPit Theatre the big black curtains that hang down either side of the stage are called ‘Legs’ and the area behind them off-stage is therefore behind the ‘leg-line’. So if you got on stage to be paid you would ‘break a leg’.