LACTICINIA. Milk (Latin, lac) and milk products, e.g., butter and cheese, and eggs or animal products formerly prohibited during Lent, along with flesh meat. In the early Middle Ages lacticinia were forbidden even on Sundays during the Lenten season.
(Hence, the origins of Carnival, Fasching, and Fat Tuesday. All the eggs, milk products and fats, whether lard or butter needed to be used up so they didn't go to waste.-JW)