An internal rhyme is a rhyme or multiple rhymes which occur within a line, rather than in the typical end-word rhyme structure. This is actually a common rhyme form, typically used in nursery rhymes. The natural associations of common sounds, usually suffixes, are typical language usage in infants, and common in most languages.
Examples of Internal Rhyme:
Jack Spratt could eat no fat|
The cat sat on the mat
Old Mother Hubbard went to the cupboard
O Frabjous Day! Kalloo Kallay!
Simple Simon met a pieman
The crazy moose is loose in the caboose