Source : Webster's Revised Unabridged Dictionary (1913)

Cachou \Ca`chou"\, n. [F. See Cashoo.]
   A silvered aromatic pill, used to correct the odor of the
   breath.

Source : WordNet®

cachou
     n : a scented lozenge used to sweeten the breath (e.g. to
         conceal the odor of tobacco)