What does the term green around the gills mean?

The term "green around the gills" is an idiomatic expression used to describe someone who looks ill, unwell, or nauseous. It suggests a pallor or sickly appearance, often associated with feeling queasy or about to vomit. The phrase likely originates from the idea that a person who is feeling nauseous might have a slightly greenish hue to their skin, particularly around the face.