The two most egregious examples, in my opinion, are Judaism and Christianity. By following the pattern and precedent shown above, we would expect the religion of "Moses-sim" or "Torah-ism" or even, "Jehovah's Witnesses". However, we are disappointed to learn that the religion of the Jews is "Judaism". This religion takes the name of one of Israel's sons and, surprisingly for a patriarchal society, not the eldest son.
Christians are called Christians, not for what they believe (that is a Modern error), but through the placing of oil (chrism) on the body. In the ancient world, the non adherents would logically call these people "Christians". The neophytes and catechumens would leave at a certain point during the liturgy so that only the "faithful" would witness the secrets or mysteries of the church.
The outside world would know NOTHING of Jesus. This where the term "mystery religion" was appropriately applied to the church. This term does not originate from the "pagan religions" that date from the 15 and 16th centuries. The knowledge of the Gospel and Epistle readings were for the initiated faithful only. There were no "Bibles" that combined the Old Testament readings with New Testament readings until 1516. If a church would be violated (as during a time of war), the soldiers would see the icons of Jesus and the Saints and candles placed before them. It is understandable that certain people would consider this idolatrous. Additionally, the faithful would need to maintain a "good standing" with the church in order to take the sacraments, notably Reconciliation.
The remission of sins is granted by the priest during confession. The remission of sins is not forgiveness, as Protestants misunderstand it. Communion unites all the living faithful with the all departed faithful. It can now be understood why the Roman Church does not know how many Masses it takes to be saved. Henry of England went to Mass five times a day. We can now understand why the selling of Masses was a source of income for the Roman Church. Indulgences (which guaranteed the release souls from Limbo) were introduced later.
Ex ecclessia nulla salus-"outside the church there is no salvation" is now understood as a phrase that was formally used by a large organization to baptize the world and now, in the quest for equality among faiths, has repudiated using it. This phrase, it seems to me, was originally used by the church in its nascence and is only appropriate for a small group (a minority of the population) to utilize, in addition to secrecy, degrees and mystical aspects, to get willing converts. The degrees can be construed as neophyte, catechumen, the faithful, deacon, priest and bishop.
Fast forward to the present age and we find there is no mystery or secret teaching in churches. Everyone knows about Jesus, and his mission, and Saint Paul, and his writings, due to printing of the "Bible" and "evangelizing" by certain people. If one were to state that there was a mystery teaching within Christianity, that person would receive untold derision, because everyone has always know everything about Christianity. We should no longer wonder why people do not go to church as frequently as previous generations, funerals and weddings excepted. The mystery is, in a word, absent.
In the Modern Age, we posses the Bible and we no longer need the Church that preserved those writings for centuries. With Protestantism, we do not need priests to hear our confessions, because we deal directly with Jesus. There is no doubt,gentle reader, that some people even bypass Jesus and pray to God. At this point, the Church, the priest and the Bible are irrelevant since they are impediments to our chats with the Deity. The openness of Modernism has brought this crisis of faith to Western Civilization and there is no returning to the past.