jic others also wondered about the georgetown history prof, carrol quigley's connection to the historically more significant carrols:

Quigley does not descend directly from those Carrolls, the landed Marylanders who were influential enough in the Revolutionary years to have a signature on the Constitution. Instead, Quigley’s maternal ancestors were the less affluent Carrolls left behind in Ireland who only got around to making it to Halifax a few generations ago. On his father’s side, the Quigleys were so poor they couldn’t even wait for the potato famine to leave Ireland for Boston in 1828.

http://www.carrollquigley.net/biography/The-Professor-Who-Knew-Too-Much.htm

but maybe they were the same family back in ireland?