The Collaborative International Dictionary of English v.0.48:

Cinnamic \Cin*nam"ic\, a. [From Cinnamon.] (Chem.)
   Pertaining to, or obtained from, cinnamon.
   [1913 Webster]

   Cinnamic acid (Chem.), a white, crystalline, odorless
      substance. C6H5.C2H2C2H2.CO2H, formerly obtained from
      storax and oil of cinnamon, now made from certain benzene
      derivatives in large quantities, and used for the
      artificial production of indigo.
      [1913 Webster]