"Esoterica" simply means that there are two faces of a teaching in a given group/sect: an outer and an inner. The outer teaching is for people not belonging to the given group/sect. The inner teachings - called the "Mysteries" [as in Mystery Schools] in ancient classical pagan times - were secret interpretations or secret meanings saved for those who are in the group/sect. And so Jesus once said in the Bible:
And so, in ancient times, in the Christian religion, there were secret interpretations to what the Bible taught openly. That would be called the "esoterica" of such a Christian religion.
By its very definition, it is not possible to logically talk about "esoterica" minus a group/sect, because esoteric means the private or secret meaning/interpretation of ideas, similes, symbolism, allegories, parables, of a group or sect.
An good example would be the Jewish Tanakh which has open/overt teachings, but such Jewish religion/sect has secret interpretations of the Tanakh which we today refer to as the Kabbalah, Gematria, etc. And so, the "Kabbalah" by definition is the "esoteric" teachings of certain Jewish sects: meaning that certain Jewish sects give ideas, allegories, and parables in the Tanakh different meanings and interpretations to their private group of fellow sectarians.
There can be no "inner teaching" of a group or sect, unless one is speaking of a specific group or sect which has secret re-interpretations of overt and open teachings.
You have to speak about Esoterica contextually, or the word "esoterica" has no meaning. Because no group/sect = no inner teaching.
An example: Euclidian Geometry.
Overtly Euclidian Geometry is a mathematical discipline which studies shapes and angles, and so on.
But the Freemasons re-interpret Geometry to have a different meaning which they do not openly teach.
Thus, Freemasonry is the contextual group/sect we are talking about. Therefore, the Freemason's "inner teachings" would be referred to as "Masonic Esoterica."
The historical context further helps gives clues as to how masonic esoterica is esoterically re-interpreted. The historical context is that, learned men during the Age of Enlightenment had rejected the Bible and its fictional stories, and many became Deists. Many of those Deists found their way into Freemasonry. The first clue is Deism and concepts circulating during the Age of Enlightenment. This was also the period when the Philosophy of Science, Natural Philosophy, and Scientific Empirical Epistemology was born.
The second clue is the letter G, which is important in Freemasonry. The letter G simultaneously stands for BOTH God & Geometry. Which echoes the world-model of the Deism during the Enlightenment were it was believed that "God" and Nature are one and the same. And so the "esoteric" interpretation of the letter G is that God and the world of shape and form [geometry] is the same thing at the same time.
From those clues and hints, and context of time and place, you can extract the esoterica of God and Geometry:
That Nature is governed my Laws/Doctrines/Principles, and by Geometry you come to know and understand such Laws, Doctrines, and Principles. Geometry, being composes of the [Greek] words Geo + Metry. Geo meaning Earth/World [gaia] and Metry meaning to Measure. In other words to Measure the World.
Measure meaning "divided up." Meter meaning "fundamental unit." Which esoterically is to say that: in order to come to learn and understand the Laws, Doctrines, and Principles that governs the Natural World, one must divide up the earth [Geo/Gaia] into its fundamental units/aspects/elements/parts. And in coming to an understanding of the World: you come to understand Nature's God and God's Nature. Hence the Square and Compass. Once called the "Dividing Compasses," and the Square which measures, which is to esoterically say: Divide & Measure.
And so, in order to talk about Esoterica, you need the context of a given group/sect.
A simple example of an Esoteric interpretation of Carnal stuff can be found in Tantra, called the 5 Ms: [Panchamakara]. If you are interested in the Left Hand Path, I at least encourage you to read that wikipedia link to the panchamakara. The Left Hand Path - in both India and China - have been associated with Carnality since ancient times.

