Byron Trott has a household name, provided that the household is worth a few billion dollars. Trott is a Chicago investment banker who has advised the likes of the Pritzkers and the Wrigleys. He earns their trust, friends and competitors said, because he is the soul of discretion, never leaking details of pending deals or hogging credit. Accordingly, he seldom gives interviews or takes leading roles in civic functions. Insiders said Chicago Mayor Rahm Emanuel had to twist his arm to get him to join the board of World Business Chicago, the city’s economic development promoter. And yet Trott...