Cacciucco is a fish soup from Livorno. It's a soup made with different types of cheap bony fish. They're placed, one after another, into a large pot and cooked according to their relative cooking times. It's served on slices of toast that are rubbed with garlic and get soaked with the thick fish sauce. It seems to originate from the local habit of putting together all the fish left after selling the catch of the day.
Some say the name is related to the Turkish word küçük, which means small, in reference to the size of the fish used in this Tuscan soup.