What is the origin of some common sayings?

The saying "bite the bullet" originated from injured soldiers biting on bullets to endure the pain of emergency battlefield surgery without anesthetic. The phrase "the whole nine yards" originated during World War II when fighter pilots fired an entire nine yard chain of ammunition at a single target.

The phrase "sleep tight" dates back to Shakespearean times when mattresses were attached to bed frames by ropes. To create a firmer mattress required tightening the ropes.

"Rub the wrong way" originated in the early days of America when servants regularly cleaned wood floors by rubbing them with cloths. For some floors, rubbing in the wrong direction created ill-looking streaks.