The name comes from kroshit, 'to crumble', after the finely chopped ingredients — and kvass versus kefir is a perennial Russian summer argument.
Okroshka is a cold soup of diced boiled potatoes, eggs, cucumber, radish, and bits of meat or sausage, all suspended in tangy kvass or soured kefir instead of hot stock. In summer, cafés and canteens around Moscow put it on the menu for a quick, cooling lunch.