arcane

Etymology

Borrowed from Latin arcānus (“hidden, secret”), from arceō (“to shut up, enclose”); cognate with Latin arca (“a chest”).

adj

1. Understood by only a few.
   arcane rituals
2. (by extension) Obscure, mysterious.
   arcane origins
   arcane details
3. Requiring secret or mysterious knowledge to understand.
   1997: Chris Horrocks, Introducing Foucault, page 67, The Renaissance Episteme (Totem Books, Icon Books; →ISBN A “signature” was placed on all things by God to indicate their affinities — but it was hidden, hence the search for arcane knowledge. Knowing was guessing and interpreting, not observing or demonstrating.
4. Extremely old (e.g. interpretation or knowledge), and possibly irrelevant.
   An arcane law