JoJo is a character from the Beatles song "Get Back", who moved from Tucson, Arizona to California and fancied himself a loner. JoJo also appears in the movie "Across the Universe", though the character is much different from what the song describes. He was played by Martin Luther McCoy.
I think this is a kind of cute nickname if your name is Joseph or Josephine or something. It makes me think of JoJo from "Horton Hears a Who" and the guy in the song "Get Back". If my name were Josephine I might use this as my nickname. But I can't picture this name on a grownup. Definitely best when used as a nickname and not one's full name.
There's a little kids' show called "JoJo's Circus" (or something like that). In it, JoJo is the name of a little clown girl living with her family in the circus.