Usually in pl. arcana. [L., neut. of adj. arcānus (see ARCANE) used subst. In 17–18th c. the pl. form arcana was occas. treated as sing with pl. arcanas.]
1. A hidden thing; a mystery, a profound secret.
1599. Sandys, Europæ Spec. (1632), 238. The Arcana of those their ineffable crossings and convertings.
1626. D’Ewes, in Ellis, Orig. Lett., I. 322, III. 218. Because … the anointing of his naked shoulders, armes, hands, and head, were arcana.
1646. J. Hall, Horæ Vac., 19. It is an arcanum of his Empire to conceale from us the date of our dayes.
1772. Watson, in Phil. Trans., LXIII. 14. Having … revealed the principal arcana in the manufacture of isinglass.
1864. Burton, Scot. Abr., I. iii. 133. The mysterious arcana of political intrigue.
2. One of the supposed great secrets of nature which the alchemists aimed at discovering; hence, a marvellous remedy, an elixir.
1646. Sir T. Browne, Pseud. Ep., 135. The Philosophers stone, potable gold, or any of those Arcana’s.
1689. Moyle, Sea Chyrurg., II. xxi. 76. The Quintessenses of Cloves and Colocynthis are great arcanums as to the Tooth-ach.
1796. Burke, Regic. Peace, iii. Wks. VIII. 343. The infallible arcanum for that purpose.
1821. Scott, Kenilw., xxii. (1853), 222. The pursuit of the grand arcanum.
