This character suffers from lisp.
A lisp, also known as sigmatism, is a speech impediment in which a person cannot articulate sibilants ([s], [z], [ʒ], [ʃ], [tʃ], [dʒ]). These misarticulations often result in unclear speech. This disease is mostly affects children. There are physiological and social factors that may cause a lisp. For example, a long chronic diseases, specific mouth anatomy (including the teeth broken in a fight), the unwillingness of parents to correct the pronunciation of a child, as well as heredity and more.