Break a leg

I subscribe to A phrase a Week which emails me the origin of a phrase a week and just got this week’s phrase ‘Break a leg’

I have always been interested about this phrase as I am into theatre and just last October took part in a public performance of a musical. There too everyone wished each other “Break a Leg” and not Good Luck on Opening Night. So thought of putting it down

Meaning
Said to actors for good luck before they go on stage, especially on an opening nights.

Origin
The term 'break a leg' appears to come from the belief that one ought not to utter the words 'good luck' to an actor. By wishing someone bad luck, the opposite is supposed to happen. Other superstitions are that is bad luck to whistle in a theatre, or to say the final line of a play during dress rehearsal.

The most common interpretation of 'break' in this context is, 'to deviate from a straight line', as in the cricketing term, 'off break'. That is, unstraighten the leg by bending at the knee, by bowing or curtseying.

'Break a leg' also means, 'make a strenuous effort'. There are many references to the phrase used that way, which pre-date the earliest theatrical good luck charm meaning. For example, from The Hammond Times, Indiana, 1942:
"Whatever the army or navy want, the Continental Roll [and Steel Foundry] will turn out ... Or break a leg trying."
So, it is possible that when an actor is told to 'break a leg', he/she may just be being exhorted to put on an energetic, exciting performance.