The Rat Pack Name
Funny enough, the rat pack name actually came from an insult directed at the men. One night, Humphrey Bogart came home from partying with his friends. His wife, Lauren Bacall, went downstairs, saw the drunk group of men, and said that they looked "like a god****** rat pack." Thus, the name was born!
Two Different Rat Packs
Funny enough, there were two different rat packs (technically). The group that was popular in the 1950s consisted of Humphrey Bogart, Mickey Rooney, Errol Flynn, Frank Sinatra, Nat King Cole, Cesar Romero, and Jerry Lewis. Eventually, the group devolved into the men who were popular in the 1960s... and Frank Sinatra.