JoJo
In the case of Josuke, he takes his nickname, because the second kanji of his personal name, "suke", can also be read "jo". There's an unusual "exception" with the name Giorno Giovanna, who is called GioGio. However his name in katakana is written "Joruno Jobana", to reflect the Italian pronunciation of GioGio (a "Jo" sound rather than a "Gio" sound).
Origin
Araki shamefully admits that the idea for the name, JoJo, comes from his neighborhood's local Jonathan's restaurant where him and his editor would often hold midnight meetings. The two decided the protagonist's first name would be Jonathan, and Araki, using Steven Spielberg's name as a reference, decided the last name will follow the same format, and thus Joestar was decided. Araki mentions that it was risky using this type of name, as using a foreigner name for a main protagonist at the time was considered taboo.
Araki also admits that stories such as East of Eden and the TV series, Roots inspired him to use a periodical style where the main character changes, but the story continues. Though this was not a very Jump style format for manga at the time, Araki decided to try and "go where nobody has gone before."
Non-protagonists who may be considered "JoJo"'s:
- George Joestar I
- George Joestar II
- Norisuke Higashikata IV (born Josuke)