1. Will you keep your shirt on , Bob? You won’t get there any faster if you drive too fast and cause a car accident.
2. I know you’re hungry, but dinner won’t be ready for another ten minutes. Just keep your shirt on!

Synonym: hold (one’s) horses. Antonyms: shake a leg; step on it. The expression is generally used in the imperative. It is used by an adult to children, a superior to a subordinate, or between two equals on friendly or intimate terms.