nacho business
Something that someone wants to know but it's not their problem. They're just trying to get into your business, and they're not invited.
Why do you know my secret? You're not my best friend, and you're not getting any of my secrets.
Why are you asking about my salary? You're not my boss, and you're not getting any of my money.
Why do you want to know my password? You're not my friend, and you're not getting any of my snacks.