When was the word ghetto first used?

The use of the Word ghetto dates back to about 1600 in Venice. There are various suggestions as to the origins of the Word.

In a time when some areas of Europe were expelling their Jewish population, Venice opted to allocate a part of the city to their Jewish population to isolate them from the "regular" population. This enabled the citizens of Venice to use the services of the Jewish merchants, bankers and doctors, but still have them isolated. However, in Venice the area was only expanded once and became overcrowded. Note that many of the inhabitants were not bankers or doctors, but were poor and lived by buying and selling secondhand clothes.

In the 1890s the Word, which originally referred specifically to an area which Jews had to live by law, was expanded to denote any run-down urban area inhabited by an ethnic minority. Since the 1960s this use has become widespread.

An interesting write up on the origins of the first Ghetto can be found at the Virtual Jewish History Tour web site. See the link below to access it.