The word "esoteric" refers to knowledge, concepts, or practices that are intended for a specific, often small group of people who have special interests or expertise. This knowledge is usually not widely known or understood by the general public. For instance, ancient philosophies or specialized scientific theories may be considered esoteric because they require a certain level of understanding or familiarity to fully grasp their meaning.
The term "esoteric" comes from the Greek word "esoterikos," which means "inner" or "within." This term is derived from "esoteros," meaning "more within," which implies a deeper or hidden level of meaning that is reserved for a select few.