Additionally... the term seems to originate as early as 12th century but became well known for the segregation and isolation of Jews under Nazi control or occupation, i.e: "Warsaw ghetto"...
Originally the Jewish quarter of a city, later the black slum area of an American city, now often used to mean any poor, violent and rough area of a city.
The first ghetto was in Venice. The word comes from the Italian (Venetian) 'gettare', (soft 'g'), to cast (as in casting metal) as there was a foundry in the area allocated to the Jews of Venice. German and Austrians pronounced the word with a hard 'g', a pronunciation which stuck, so that's why the 'h' was inserted, to keep the 'g' hard.