ärˈkānəm sometimes -an- or -än- noun
( plural arca·na -nə)
Etymology: Latin, from neuter of arcanus closed, secret, from arca chest — more at ark
1. : a secret or mysterious knowledge or information known only to the initiate
an arcanum of prosodic theory which is the province of specialists — P.F.Baum
certain arcana … which you must with the utmost care conceal, and never seem to know — Earl of Chesterfield
2.
[New Latin, from Latin]
: an extract of the vital nature of something : a powerful natural agent : elixir
the search of the alchemists for the grand arcanum