Jews were tolerated (what an ugly concept) in Venice, but were in fact confined for a period to this neighborhood in the sixteenth century, which has some of the tallest buildings in Venice due to the fact that they could not expand outside its confines and had to develop vertically.
There are various explanations for the origin of the word. The most popular is that the area was close to a foundry- getar being the word for "to cast (metal)". Another possibility is that it is an abbreviation for borghetto, small village. Yet another is that it comes from a Hebrew word meaning "separation."
Like practically everyone else in the world, Venice's ghetto has its own site, right here.