Idioms

Our English idioms and words don't always make sense, if you didn't grow up hearing them.  Does anyone really think buttons are cute?  Here are a few more idioms:

• A piece of cake means that something is easy.  For example, "That test was a piece of cake."
• Under the weather means to not feel well.  For example, "He's under the weather and can't go to work today."
• It costs an arm and a leg means that something is expensive.  For example, "That new toy costs an arm and a leg." 
• Break a leg means you are wishing someone good luck.  For example, "Break a leg, friend.  I'm sure you'll do great." 
• "To beat around the bush" means you're trying to avoid a difficult conversation.  For example, "Quit beating around the bush and just tell me."
• Once in a blue moon means something doesn't happen often.  For example, "I only call my family once in a blue moon." 
• To "spill the beans" means to accidentally tell a secret.  For example, "She accidentally spilled the beans about Jim's surprise party."
• To say "the ball is in your court" means it's your turn to make a move.

Can you explain any of these idioms (or share an example or two)?