This is a great work. (I am german and this is one of my fav weapons) In the middle ages only knights were allowed to own and to fight with a sword. So the langes Messer was the weapon of the "normal soldier". And because of "swords" were the weapons of the knights, they named this weapon langes Messer (long knife).
It's a pretty unclear subject since messer just means knife, but usually langes messer and krieg messer are interchangeable for the larger hand-and-a-half or two-handed saber-knives. The grosse messer or often just messer is usually regarded as the smaller types, usually for one hand. If you are familiar with the Cold Steel Grosse Messer, that is a bit of a misnomer.
Haven't really made any messers lately. Most of these older ones were made on custom order. Would like to add one for use with Durer or Talhoffer though in our current semi-production/semi-custom lineup.