(formerly) a popular name for the Hospital of St Mary of Bethlehem in London. It was established as a priory (= a small Christian religious community) in 1274, and in the 14th century it became a place for mentally ill people, who were then called ‘lunatics’. People used to come and watch the patients and be entertained by their disturbed condition. From this the word bedlam has come to mean a scene of noisy confusion:
The teacher’s whistle could not be heard above the bedlam in the playground.