History of Manchester
According to Oxford University Press, Manchester derived its name from Mamucium, the Roman name for the 1st century-settlement and fort. Mamucium itself is a Latinised form of the Celtic meaning "breast-shaped hill".
Manchester-by-the-Sea, Massachusetts
Manchester was first settled by Europeans in 1629 and was officially incorporated in 1645. It was formed out of territory taken from Salem (that portion since given to Beverly) and Gloucester.