The five family names were the names that turncoat Joe Valachi used when he testified before the McLellan comitee. They were the names of the current bosses at that time, early 60's. These names were accepted by the feds, the media and apparently the mob itself as a convienient way to refer to the families and have been used ever since. The only name to change since that time was Profaci to Columbo because leadership in that family was in transition at the time of the hearings.