I once had the good fortune of visiting with Lauren Bacall in her apartment in NYC. Somehow we got on the subject of etymology and wound up spending some time sharing knowledge with each other (read: I was 23, so she was the one doing most of the sharing, not me).
1. Break a leg
Though the real origin of the phrase 'break a leg' is debated, Ms. Bacall told me that the one she and her friends thought to be true went like this: In the days of the Globe Theatre, if an actor received enough curtain calls, s/he would be allowed to forgo the usual 5th position bow/curtsy, and actually take a knee, thereby breaking the leg line. Likewise, if money was thrown onto the stage (considered a tip, btw), they were allowed to break their leg to bend down and pick it up.
Actors hoped to receive numerous curtain calls for their performances, and so the expression break a leg became popular. Curiously, in the ballet world, dancers are understandably superstitious about breaking their legs, so instead, they mutter the French merde to each other before going out on stage. (And if you don't know what merde means, Google it!)
2. Winging it
According to Ms. Bacall, this phrase has its origins in the theater, as well. Actors who didn't know their lines very well would rely on a special prompter who stood in the wings of the theater with the script in hand. When an actor had a moment to exit the stage, he could peek at the script before his next entrance with the lines fresh in his head.
And here, finally, is one I was able to explain to Ms. Bacall. Originally, tea cups and plates were stored on a long wooden board set against a wall, much like a special table to display china. Eventually these boards were stacked on top of one another, creating open shelving, like bookshelves, which later morphed into cabinets with doors that opened and closed.
Have a word or phrase you want me to research? Drop it in the comments and I'll get to it next week!