Moat
Moat , noun
[Old French mote hill, dike, bank, French motte clod, turf: compare Sp. & Portuguese mota bank or mound of earth, Italian motta clod, Late Latin mota, motta, a hill on which a fort is built, an eminence, a dike, Prov. German mott bog earth heaped up; or perh. French motte, and Old French mote, are from a Late Latin past participle of Latin movere to move (see Move). The name of moat, properly meaning, bank or mound, was transferred to the ditch adjoining: compare French dike and ditch.]
(Fortification) A deep trench around the rampart of a castle or other fortified place, sometimes filled with water; a ditch.
Moat , transitive verb
To surround with a moat. — Dryden