arcana means specialized knowledge that is mysterious to the uninitiated. Lexicurio rates it Rare gem — a strength score of 84 out of 100.
arcana is pronounced /ɑɹˈkeɪnə/.
Why “arcana” is a great word
ARCANA — [Noun] Specialized knowledge that is mysterious or secret to the uninitiated. From Latin arcānus ("hidden, secret"), from arcēre ("to withhold, keep away"), from arca ("a chest, box"). First recorded in English use 1600–10. Unlike "arcane" (which describes the quality of such secrecy) or "esoterica" (which catalogs the items themselves), arcana is the hidden substance, the guarded contents of the locked chest. It is the cipher in a grimoire's margin, the whispered liturgy of a closed rite, and the proprietary algorithm humming in a server farm—the collective gravity of all that is deliberately kept from the light, a testament to the human impulse to create mysteries as much as to solve them.
Etymology
From Latin arcānus (“hidden, secret”), from arcēre (“to withhold”), arca (“a chest”).
noun
- Specialized knowledge that is mysterious to the uninitiated.“Thou deign'st no answer,—or I fain would ask
If since thy bright creation, thou hast seen
Ought like a Newton, whose admitted eye
The arcana of the universe explored
Light's subtle ray its mechanism disclosed,
The impetuous comet his mysterious lore
Unfolded,”