caryocar butyrosum

from The Collaborative International Dictionary of English v.0.48

Butternut \But"ter*nut`\, n.
   1. (Bot.) An American tree ({Juglans cinerea}) of the Walnut
      family, and its edible fruit; -- so called from the oil
      contained in the latter. Sometimes called {oil nut} and
      {white walnut}.
      [1913 Webster]

   2. (Bot.) The nut of the {Caryocar butyrosum} and {Caryocar
      nuciferum}, of S. America; -- called also {Souari nut}.
      [1913 Webster]