arcanum

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."