He couldn't not when the man who proclaimed himself Sir Guy of Gisborne made the off-color comment of never touching a man's sword without his permission. Sword. The only immediate and relevant thought flowing through Jack's mind was that he always got permission to touch a man's 'sword' if he wanted to touch it...
But then he remembered he was standing on a street corner with a dirty, deranged sort of man who had been wielding and actual medieval sword. Then Jack giggled again. Sir Guy of Gisborne. If the 'Sir' hadn't made him laugh, which it did, the 'Guy' certainly did. Honestly, couldn't this Rennie come up with a better name to use than Guy? Sir, at that.
Sir Guy.
Sirguy. Serguy. Sergi. Hadn't Jack dated a Sergi at one time? Maybe that was the man's name. Sergi Gisborne. Maybe he wasn't a Rennie. Maybe he was just some man in the street dressed funny, with a medieval weapon whose name was Sergi Gisborne.
"Couldn't tell you which country, Sergi, but the City is only known as The City."