I use the terms esoteric and exoteric quite frequently. The exoteric is knowledge about an external, reproducible world, essentially science but includes our phenomenal perceptions.
In contrast, esoteric knowledge is about the inner world that, so far, at least, remains personal and has proven difficult to formalise scientifically. It is about those experiences that others cannot perceive. Thus, knowledge about the esoteric world is a form of exoteric knowledge, but esoteric experiences are truly esoteric.
Such wisdom is not "hidden" in the sense that you are not told the correct incantation, it is only hidden because few choose to deliberately dwell in that space.
For most people, like myself, such experiences first happen by accident, and for those who do not back away, the rabbit-hole beckons.
That's an another aspect to look at it as, thanks ;)