Cerberus was an planet in the Cerberus system, where a Federation colony was established some time prior to 2259.
In that year, that settlement experienced a crop failure and the entire population was in jeopardy of starvation. Fortunately, the population was saved when noted philanthropist, Carter Winston, used his personal fortune to bring in enough food and goods to carry the colony through the crisis. One of the people saved was Joanna McCoy, the daughter of Leonard McCoy. (TAS: "The Survivor")
According to Startrek.com, the planet was named after Cerberus, the three-headed dog that guarded the gate to Hades in Greek mythology. [1]
According to the Star Trek: Star Charts ("United Federation of Planets I"), in 2378, Cerberus was a Federation member.