c.1600, from Modern Latin laudanum (1540s), coined by Paracelsus for a medicine he mixed, supposed to contain gold and crushed pearls and many expensive ingredients, but probably owing its effectiveness to only one of them, opium. Perhaps from Latin laudare "to praise," or from Latin ladanum "a gum resin," from Greek ladanon, a word perhaps of Semitic origin. The word soon came to be used for "any alcoholic tincture of opium." Latin ladanum was used in Middle English of plant resins, but this is not regarded as the source of the 16c. word.
laudanum lau·da·num (lôd'n-əm)
A tincture of opium, formerly used as a drug.