Giacamo Justerini is the man that first started the J&B brand when he fell for on Opera singer named Margherita Bellini and followed her to England. Sadly this isn't that kind of love story where they run off together and start a Whisky brand but Justerini is where the 'J' from J&B comes from.
However from this Justerini was introduced to his future business partner George Johnson (so it isn't all bad). Two generations of Johnson's go by and Alfred Brooks buys the company and renames it J&B (and now we have the 'B'). The partners task a man named Andrew Usher with making a drink which is smoother and better than the original and he does just that, this eventually became the J&B Rare Whisky!