From LoveToKnow 1911 : http://www.1911encyclopedia.org/Laudanum
LAUDANUM, originally the name given by Paracelsus to a famous medical preparation of his own composed of gold, pearls, &c. (Opera, 1658, i. 492/2), but containing opium as its chief ingredient. The term is now only used for the alcoholic tincture of opium (q.v.). The name was either invented by Paracelsus from Lat. laudare to praise, or was a corrupted form of "ladanum" (Gr. X 5avov, from Pers. ladan), a resinous juice or gum obtained from various kinds of the Cistus shrub, formerly used medicinally in external applications and as a stomachic, but now only in perfumery and in making fumigating pastilles, &c.