Where appeared the first Ghettos? Why?

from:http://www.wordiq.com/definition/Ghetto

The first ghettos appeared in Germany, Spain
and Portugal, in the 13th century, but some authors use the same word to indicate the destination towns to which the Roman Empire deported Jews from the first to the fourth centuries CE.

The term ghetto comes from Venice's Ghetto in the 14th century. Before the designation of this part of the city for the Jews it was an iron foundry (getto), hence the name. Other etymologies suggested for the word include the Italian borghetto for "small neighborhood" or the Hebrew word get, literally a "bill of divorce." From the example of the Venice Ghetto the name then transferred to Jewish neighborhoods. In Castile, they were called Judería and in Majorca, call. It is worth noticing that the gated Jewish quarter in Venice (the Ghetto), was an affluent part of the town inhabited by merchants and moneylenders. Non-Jews were not allowed to live in this ghetto, and the gates were locked at night.

Thanks for the question, Mozart; didn't know that.

Good answer Kelleygirl. You can also found other details on this site..