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early 14c. (late 13c. in place names), "ditch, trench," mid-15c., from Old French fosse "ditch, grave, dungeon" (12c.), from Latin fossa "ditch," in full fossa terra, literally "dug earth," from fem. past participle of fodere "to dig" (see fossil).
The Fosse-way (early 12c.), one of the four great Roman roads of Britain, probably was so called from the ditch on either side of it.