Dummy Shareholder
  
Anyone play bridge? Oh, you're not ninety? Okay.
Well, there are four players and one sits out to be the, uh, dummy. In the case of bridge, that's the guy or gal who gets the coffee, the donuts, the fake creamer.
In the realm of shareholding, a dummy is just a placeholder for another. Or said another way, the dummy is the one sitting in to hold shares in a company for the benefit of another.
Like...what if an uber-duper-religious investor really wanted to buy shares in a tobacco or gambling company, but didn't want it known that she was doing so? Dummy time. And then donut time.