Emily Dickinson Lexicon

DUN'GEON, n. [Fr. dongeon, or donjon, a tower or platform in the midst of a castle, a turret or closet on the top of a house. In one Armoric dialect it is domjou, and Gregoire suggests that it is compounded of dom, lord or chief, and jou, Jupitor, Jove, an elevated or chief tower consecrated to Jupiter; but qu. In Scottish, it is written doungeoun, and denotes the keep or strongest tower of a fortress, or an inner tower surrounded by a ditch. Jamieson. It was used for confining prisoners, and hence its application to prisons of eminent strength. The dungeon was in the bottom of a castle, under ground and without light. – Henry. Brit.]

1. A close prison; or a deep, dark place of confinement. And in a dungeon deep. – Spenser. They brought Joseph hastily out of the dungeon. – Gen. xli.
2. A subterraneous place of close confinement. – Jeremiah.