white-shoe investing firm??

"Few have ever accused Morgan Stanley, the white-shoe investment bank formed in 1935 by partners of the imperial J.P. Morgan & Co., of being solicitous toward the investing masses. "

This is from a magazine. What is “white-shoe”? From the context it means elite, like “silk-stocking”, but why white shoes?

White bucks, worn in the summer with a seersucker suit. Very top drawer (at least here in the South).