My favorite source on Francis has always been G.K. Chesterton's "St. Francis of Assisi."  I always have assumed that Francis' given name - the one he gave back to his father standing there naked in his birthday suite - is/was Giovanni di Bernardone.  

Chesterton does a great job of telling the story of the psychological and spiritual transformation from Giovanni ["le troubadour" or lead singer of the medieval traveling troupes] to Francesco (actually means "little Frenchy," a nickname really), the self-described "le Jongleur de Dieu" or the clown or jester of God.  Francesco's becoming "le jongleur" allowed him to embrace the freedom he gained from evangelical poverty so he could now sing of "Brother Sun, Sister Moon."

[I came across these themes when studying the "History of Theater and Drama" - specifically medieval theater.  Francesco as a singing poet was certainly familiar and consistent with this artistic genre.]