This is the accompaniment to rigaglia, Pistoia's traditional boiled offal (veal). It's a soup (Italians would call it a pappa, or 'pap') made with the broth from cooking the stuff, along with some carrot-celery-onion and maybe tomato, greens, etc, and lots of stale bread. Modern version add garlic and cheese, but it's seldom seen in Pistoia's trattorias.
The unusual name comes from a prison (carcere) in Pistoia next to the slaughterhouse. Back in the 15th century prisoners asked if they could have the bits of offal the neighbouring slaughter house was throwing away, and add them to their thin soup. They would get some every week, if they behaved.
Image by Agriturismo Podere Santa Rita