It is believed to have been built, around 250 BC, by the Dobuni who were one of the Celtic tribes living in the British Isles prior to the Roman invasion of Britain. The name Maes Knoll is derived from the Brythonic word "maes" meaning "flat top", derived from Latin "mensa" meaning "table.", and Old English "knoll" or "knowle" meaning "hill". The existing scarp slopes were steepened and, on the north-western edge of the fort is an earthen mound, known as Maes Knoll Tump, about above the rests of the fort defences, which is across and above a defensive ditch.