The Collaborative International Dictionary of English v.0.48:

Damiana \Da`mi*a"na\, n. [NL.; of uncertain origin.] (Med.)
   A Mexican drug, used as an aphrodisiac.
   [1913 Webster]

   Note: There are several varieties derived from different
         plants, esp. from a species of Turnera and from
         Bigelovia veneta. --Wood & Bache.
         [1913 Webster]