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Webster's Dictionary (1865)

Ar-cā'num, n.

noun

n.; pl. AR-CĀ'NA. [Lat. arcanum, from arcanus, closed, secret, from arca, chest, box, from 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.) A secret remedy reputed to be very efficacious. Dunglison.