Why are nurses called sisters?
In medieval Europe, hospitals were run by monasteries, and monks attended to the patients.
In the sixteenth Century, Henry VIII of England destroyed most of the monasteries in England. This forced nuns (sisters) to attend to the patients and ever since nurses have been called sisters.
Nun, 'ninne' in old English, is derived from Latin 'nunna' or 'nonna' and means 'an old maiden lady'.