Josie is jaunty and friendly: among the most winning of all nickname names. She has never NOT been on the Social Security list since records began being kept, and is now at its highest--Number 254--since 1910.
Josie and the Pussycats , revolving around an all-girl pop band, as been a pop culture phenomenon for decades, in comic books in the sixties, a Saturday morning animated cartoon series in the seventies, and as a live action movie in 2001. In a recent romcom, Drew Barrymore's character mentions that she was named after that Josie.
While Josie is the most stylish short form for Josephine, Jo, Feeny, and even Fifi are other possibilities.