ARCANUM
secret, arcanum
(noun) information known only to a special group; “the secret of Cajun cooking”
Source: WordNet® 3.1
Etymology
Noun
arcanum (plural arcana)
A mystery or deep secret.
An elixir or secret remedy.
Source: Wiktionary
Ar*ca"num, n.; pl. Arcana. Etym: [L., fr. arcanus closed, secret, fr.
arca chest, box, fr. arcere to inclose. See Ark.]
1. A secret; a mystery; -- generally used in the plural.
Inquiries into the arcana of the Godhead. Warburton.
2. (Med.)
Definition: A secret remedy; an elixir. Dunglison.
Source: Webster’s Unabridged Dictionary 1913 Edition