The first ghetto was established in 1516 in Venice, Italy. Jewish residents were forced to live in a small industrial area by the government and locked in at night. Here is a picture of a ghetto map from I took while there a few weeks ago.
According to the sign Jews were only allowed to work as doctors, money lenders or second hand clothing sellers. The ghetto was expanded to two squares, the Ghetto Vecchio (old, which is actually the newer one) and Nuovo (new). After the French took over Venice in 1797, Jews were finally allowed to freely move about the city but this area remained a center of Jewish culture. It still is despite most of Venice’s Jews having been murdered in the Holocaust. There are still a handful of restaurants and places of worship.
The origins of the word ghetto are disputed. It could mean foundry, street, little town or “throw away” depending on which theory you choose. Here is a simplified (but also hard to read) map of the area by artist Gianluca Costantini.