Hmm. Anyone know when this doctrine first showed up, or was made official by the church? It isn't found in Scripture
Actually, the concept of pergatory dates back to pre Christian days and based on early old testament books. These books or as Protestants refer to them as the Apocrypha were accepted teaching by the Church and part of the Vulgate, the Latin translation of the Bible by St. Jerome. Luther had them removed partly due to their references to pergatory.