arcanum
noun
ar·ca·num är-ˈkā-nəm 
plural arcana är-ˈkā-nə
1
: mysterious or specialized knowledge, language, or information accessible or possessed only by the initiate —usually used in plural
2
: elixir sense 1
Did you know?
The word arcanum (pluralized as "arcana") came from Latin arcanus, meaning "secret," and entered English as the Dark Ages gave way to the Renaissance. It was often used in reference to the mysteries of the physical and spiritual worlds, subjects of heavy scrutiny and rethinking at the time. Alchemists were commonly said to be pursuing the arcana of nature, and they sought elixirs for changing base metals into gold, prolonging life, and curing disease. The frequent association of the word with the alchemists' elixirs influenced the use of "arcanum" for "elixir."
Example Sentences
Recent Examples on the Web What became clear is that even publishers, agents, and retailers, who’ve rightly been focused on signing writers and selling books, didn’t appreciate how much the arcana of the business would matter in the move to digital platforms. 
Tim Carmody, WIRED, 3 Aug. 2010
Tim Carmody, WIRED, 3 Aug. 2010 Word History
Etymology
Latin, from neuter of arcanus secret, from arca chest — more at ark
First Known Use
15th century, in the meaning defined at sense 1