A bump on the head, especially on a child, is commonly called a goose egg because the shape of the bump is similar to that of a small egg. When a child hits his head, the goose egg results from fluid and blood leaking from the scalp.
Although a goose egg can have an unpleasant appearance, most bumps to the head are harmless as long as they are not accompanied by neurological changes, states ChildrensMD.org. Seek medical assistance right away if the child loses consciousness or appears drowsy or confused. Eye size changes, inability to walk and move normally, fluid leaking from the nose or ears, or vomiting more than two times are also signs that professional medical attention is needed.