The term Duke or Earl is a TITLE given to a NOBLEMAN, a member of the peerage. The term is used to refer to a person of high social rank, usually a member of the aristocracy. The term is derived from the Latin dux, meaning leader, and comes from the Middle English word eorl, meaning a man of NOBLE birth. The TITLE is also used to refer to a person who holds a hereditary TITLE of nobility, such as a Duke or an Earl. The TITLE is often used to denote a person of high social standing, and is often used in conjunction with other titles, such as Lord or Lady.