In historical context there would basically be two sides to a Mystery. There is the exoteric side which revolves around the rites, ceremonies and beliefs regarding the Mystery and then you have the esoteric side which corresponds with adept understanding and study. To progress from the outer order to the inner order one had to complete the work of the outer order.
To the people, they saw them as the initiates whom would first study in public and learn all of the exoteric features of the Mystery and then they would graduate to the inner order and begin to work on the true secrets of the Mystery which are discovered only internally. Hence the 'Mystery School' which is both exoteric and esoteric is called as such because of its association with some great Mystery of the universe and less so because of its secrecy.
The truth is the secrecy is more something put in by elitist mindset to reserve it for those of power. This has convoluted the idea somewhat.
I've seen it suggested that at one point 'Right Hand Path' corresponded with the exoteric work and 'Left Hand Path' corresponded with the esoteric work. Hence the corruption of the concept of the Left Hand Path being negative almost seems like a clever confusion to keep people away from inner orders.
To the people, they saw them as the initiates whom would first study in public and learn all of the exoteric features of the Mystery and then they would graduate to the inner order and begin to work on the true secrets of the Mystery which are discovered only internally. Hence the 'Mystery School' which is both exoteric and esoteric is called as such because of its association with some great Mystery of the universe and less so because of its secrecy.
The truth is the secrecy is more something put in by elitist mindset to reserve it for those of power. This has convoluted the idea somewhat.
I've seen it suggested that at one point 'Right Hand Path' corresponded with the exoteric work and 'Left Hand Path' corresponded with the esoteric work. Hence the corruption of the concept of the Left Hand Path being negative almost seems like a clever confusion to keep people away from inner orders.