to not be able to keep still because you are very excited or worried about something
nie móc usiedzieć w jednym miejscu
She's got ants in her pants because she's going to a party tonight.
My six year-old son has ants in his pants because he is going to watch a football match tomorrow. He’s so excited.
Martha had ants in her pants because she had a presentation to give in her business class.
Ciekawostka
Przymiotnik antsy czyli nerwowy, podenerwowany wywodzi się właśnie od tego idiomu