What is a one letter word for a kangaroo pouch?

Kangaroos are marsupials and, like most (but not all) marsupials, they have a pouch, which is actually called a marsupium. This is positioned at the lower front of the abdomen. All baby marsupials, known as 'joeys' are born very undeveloped after a short gestation period, so they continue to develop in the marsupium, or pouch, for many more months. The purpose of the marsupium is to protect the joey until it has developed enough whereby it can look after itself.