Americans normally think of a "ghetto" as a section of a large city that is a rundown, dilapidated, rat-infested slum inhabited by one ethnic group that has been forced to live there because of discrimination or institutionalized racism. In former times in Europe, "ghetto" was the term for a walled section of a city where the Jews were forced, according to the laws of the city, to live separately from the Christians. Because of over-crowding and isolation, these ghettos usually turned into slums. So when the Germans turned the town of Theresienstadt into a Jewish ghetto in November 1941, this was not by any means a  innovation. Even before the word ghetto came into use, and long before the s came upon the scene, the Jews were eventually segregated into a ghetto in almost every city where they settled. Usually they were already living in a separate part of the city, known as the Jewish quarter. These segregated quarters became ghettos only after walls were erected, a curfew for the Jews was established, and the Jews were forced to wear distinctive clothing to instantly identify themselves to non-Jews.
The word "ghetto" derives from the name of an area of the city of Venice where the city's foundries were located. In the Venetian dialect, a foundry was known as a "geto" which meant a workshop or a factory. The word "geto" was derived from the verb "gettare" which means "to cast" as in to cast iron in a foundry.
After the Jews were expelled from Spain in 1492 and from Portugal in 1497, many of them settled in Venice. In 1516, a city decree forced the Jews of Venice to live on a small island with only two access points which were sealed off at sunset. This island had previously been the area of the "gheto nuovo" or new workshops.
However, even before the word ghetto came into use, the Jews, particularly in Poland, were confined to walled sections of the city where they lived. In 1492 the Jews of Krakow in Poland were put into a walled-off section after they were accused of setting fires in the city. There were no walled Jewish ghettos in the Old Reich, as Germany proper was called, during Hitler's regime. Hitler sent the German Jews to the Lodz ghetto, located in what had formerly been Poland or to Theresienstadt, located in what was formerly Czechoslovakia.
The second Jewish leader of Theresienstadt was Dr. Paul Eppstein who was taken to the Small Fortress on September 7, 1944 and immediately shot without the benefit of a trial because he too disobeyed the orders of the s. The last Jewish leader of the ghetto was Dr. Benjamin Murmelstein, who served from Sept. 7, 1944 until the end of the war. The ghetto guards were 150 Czech policemen; there was also an unarmed Jewish ghetto guard unit which helped to maintain order in the ghetto. On the wall near the entry door to the Museum in the Magdeburg building, there is a plaque which lauds the Jewish leaders in the ghetto for their resistance against the s, even though it meant death for two of the Elders.
*source: wikipedia.org, scrapbookpages.com