from The Century Dictionary.
- Noting a large bog or lake in Egypt, lying between the Delta and the Isthmus of Suez.
from the GNU version of the Collaborative International Dictionary of English.
- adjective Relating to the lake of Serbonis in Egypt, which by reason of the sand blowing into it had a deceptive appearance of being solid land, but was a bog.
Sorry, no etymologies found.
And there, whether it be in the light that beats on God's great throne, or in the serbonian darkness of a hell more horrible than that pictured by Dante -- is the true Heaven.