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
The name change was driven by Edward Corley, a longtime resident of Manchester. All town documents, and the town seal, now use the name "Manchester-by-the-Sea", and as a result of some minor resident activism, so do the majority of public and private lists of Massachusetts cities and towns, including that of the state government.