Source : Webster's Revised Unabridged Dictionary (1913)

Tonka bean \Ton"ka bean`\ [Cf. F. onca, tonka.] (Bot.)
   The seed of a leguminous tree ({Dipteryx odorata}), native of
   Guiana. It has a peculiarly agreeable smell, and is employed
   in the scenting of snuff. Called also {tonquin bean}.
   [Written also {tonca bean}, {tonga bean}.]