Ever heard the phrase sitting on a time bomb? Which might I add would explode anytime? Not actually sitting on a bomb, but maybe when you committed an offense and you're waiting for whoever is in charge to issue their verdict. For example say back at high school you or that notorious classmate of yours committed an offense and was called into the principal's office.
Sitting squirm-ishly in the seat facing the principal as they kept glaring at you behind their thick glasses with a bald head. You knew you are wrong and you are waiting for them to issue their punishment but they didn't say anything and the suspense is killing you? That's when your stomach would go knots and you'll have that urge to visit the toilet.
Yeah, that's exactly what the feeling of sitting on a ticking bomb is.
