A kangaroo's pouch is called a marsupium. The word is derived from the Latin word "marsuppium," which means a purse or a pouch. A kangaroo is a marsupial, an animal with an external pouch in which offspring suckle and develop, according to Dictionary.com.
Unlike mammals, marsupials do not nourish their embryos through a placenta attached to the mother. Instead, marsupials are born at a much earlier stage than mammals and continue their development within the pouch. When first born, marsupials have underdeveloped eyes, ears and rear limbs. However, the forelimbs, nose and mouth are fully developed to allow them to move to the pouch and latch onto their mother's nipples so that they can feed and continue to develop.