Here are some ways to understand its meaning:
* Secret plan: You might say "I'm not sure what he's got up his sleeve, but I'm sure he has a plan." This implies that someone is secretly working on something, but they haven't revealed it yet.
* Surprise: You might say "I'm excited to see what they have up their sleeve for the party." This means you are expecting something unexpected or exciting to happen.
* Trick or deception: The idiom can also be used in a negative way to suggest that someone is being deceitful or manipulative. You might say "Don't trust him, he always has something up his sleeve."
Origin:
The idiom likely originated from the practice of magicians who would hide objects up their sleeves to use for their tricks.
Examples:
* "The candidate has a few surprises up her sleeve for the upcoming debate."
* "I'm not sure what the boss has up his sleeve, but I'm a little nervous about the meeting."
* "The detective knew the suspect had something up his sleeve, but he couldn't figure out what it was."