What Does the Expression “Clean Bill of Health” Mean and Where Did the Idiom Come From?

If you say a doctor has given you a clean bill of health, you’re using a nautical expression.

The phrase comes from the days when sailing ships were required to obtain a document from local officials at every port of call declaring that they had not been exposed to any epidemic or infectious disease.

If they didn’t have this bill of health, the next port would quarantine the ship, crew, and cargo for forty days.