In the years of Anglo-Saxon rule, an alderman was the viceroy, or representative ruler, who governed a kingdom, district, or shire for the king. The term has also been used for the mayor's second in command in a county or borough in England or Ireland.
In some U.S. cities, alderman refers to a member of the municipal legislative body. Chicago, for example, has an alderman to represent each of the 50 wards in the city.
Alderman derives via Middle English from the Old English ealdorman, from ealdor, the word for "parent" that related to our words old and elder.