Within a Budding Grove (vol II pp 449...) French noble titles - Notes for July 2011

From a rather interesting article on French nobility and/or titles over at Heraldica.org:
"The origin of modern titles like duke, marquis, count lie in public offices held under Merovingian kings (6th-8th c.).

• A duke (Latin dux, literally "leader") was the governor of a province, usually a military leader.
• A count (Latin comes, literally "companion") was an appointee of the king governing a city and its immediate surroundings, or else a high-ranking official in the king's immediate entourage (the latter called "palace counts" or "counts Palatine").
• A marquis was a count who was also the governor of a "march," a region at the boundaries of the kingdom that needed particular protection against foreign incursions (margrave in German).
• A viscount was the lieutenant of a count, either when the count was too busy to stay at home, or when the county was held by the king himself.
• A baron (a later title) was originally a direct vassal of the king, or of a major feudal lord like a duke or a count.
• A castellan (châtelain) was the commander in charge of a castle.  A few castellanies survived with the title of "sire."

"An edict of 1575, rarely enforced, established a minimum size and income for the land to which the created title was attached, thus establishing a hierarchy which was purely notional:

• duc (duke)
• marquis (marquis)
• comte (earl)
• vicomte (viscount)
• baron (baron)"