What does pu mean in junie b Jones?

In Junie B. Jones books, "PU" is an abbreviation for "Pull-Ups." Pull-Ups is a brand name for disposable training pants or diapers that are designed to help children learn how to use the toilet. In the books, Junie B. Jones is often reluctant to give up her diapers and transition to using Pull-Ups, so the term "PU" is used to refer to them in a humorous way.