Various theories have been put forward as to the origins of the name Loudoun. One such theory is that the name was originally used in reference to Loudoun Hill, being a combination of two Scots words law and dun, which roughly translates as Firehill. Another Loudoun Hill theory is that the name was originally Lugudunon, which roughly translates as The Fortress of Lugh. It has also been speculated that the name simply derives from the Celtic word, Loddan, which means marshy ground.