More than half a century after their heyday, the term "Rat Pack" still conjures up images of Frank, Sammy, and Dean. But the phrase didn’t originally refer to the group of guys most people think it does—and actually, it wasn’t even a group of all guys.

Originally, the group centered around Humphrey Bogart and his pals: Judy Garland, David Niven, Angie Dickinson, talent agent Swifty Lazar, restaurateur Mike Romanoff, and, of course, Frank Sinatra.

According to Stephen Bogart, son of Humphrey and Lauren Bacall, the term originated when his mother walked in on his father and the rest of the group during a particularly drunken weekend in Las Vegas. “You look like a goddamn rat pack,” she told the disheveled group. They found it hilarious, and when she repeated the phrase a few days later, it stuck.

As one of the most exclusive clubs in the world, the Rat Pack had its own coat of arms (a rat gnawing on a human hand) and its own motto (“Never rat on a rat”). They even assigned themselves titles: Sinatra was the Pack Master, Bacall was the Den Mother, Garland was Vice President, her husband and manager Sid Luft was the Cage Master, Lazar was Treasurer and Recording Secretary, and Bogart was in charge of PR—though Stephen Bogart said his father’s role was more akin to “spiritual leader.”

“You had to stay up late and get drunk, and all our members were against the P.T.A. We had dignity. And woe betide anyone who attacked one of our members. We got them,” Bacall once said.

Following Bogie's death in 1957, Sinatra became the de facto leader, spiritual and otherwise. The group consisted of his closest cronies, the ones who are most associated with the term “Rat Pack” today—Dean Martin, Sammy Davis Jr., Peter Lawford, and Joey Bishop. Reportedly, this incarnation of the gang simply referred to themselves as “the Clan,” not the Rat Pack. In fact, during a 1987 announcement of a reunion tour called “Together Again,” Sinatra chided a reporter for using “that stupid phrase.”