Butternut

But·ter·nut

Butternut

n.
  1. 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. (Bot.)
  2. The nut of the Caryocar butyrosum and Caryocar nuciferum, of S. America; -- called also Souari nut. (Bot.)