Ever since the Truman administration, the White House Communications Agency—a branch of the military—has assigned Secret Service nicknames to Presidents, First Families, and other Washington royalty. Though these titles are largely ceremonial now, they reveal much about the men and women behind the monikers.

Photographs by Bloomberg (2); Alamy (3); Everett; Getty Images (8). Data: The Secret Service; The Hidden History of an Enigmatic Agency; A History of the Presidents and Their Planes