Complex sentence: The series'title is a reference to the fact that each part's main character's name can be read as "JoJo", a nickname derived by putting together the letters "J" and "O" from their first and last names.
Split into simpler sentences: The series'title is a reference to the fact that each part's main character's name can be read as "JoJo". A nickname derived by putting together the letters "J" and "O" from their first and last names.