There was an answer before this one that was removed because of placeholder rules and I meant to reply to it, but it was talking about the écorcheurs, meaning 'flayers' in English, who roamed France in the anarchy of the 15th century when the country was split in two. It is uncertain how they received their name. It could be figurative in that they stripped the land of all its 'skin', its goods and resources, or could be more literal, that they skinned their victims alive.

The écorcheurs could be absolutely brutal, as shown when they threw their support behind the Burgundians in 1418 and massacred the Armagnac faction in Paris. First setting fires and erecting barricades, they besieged the houses owned by Armagnacs in the city. When it became clear that the écorcheurs would get in, many Armagnacs threw themselves into the Seine rather than get captured by them.

It gets a bit disgusting after this. My source records that the écorcheurs broke in and gave those that remained a 'supplice d'une lente agonie', a torture of slow death. The Armagnac men were flayed and had their members mutilated before being stabbed and thrown in the Seine. The women were dragged naked from their beds and subjected to all manner of abuses then being cut open. A pregnant woman was said to have had lost her unborn baby in this way.

The écorcheurs therefore seem to have been just as depraved and wicked as the modern Mexican cartels.

Source: Charles-Victor Prévôt d' Arlincourt, Les Écorcheurs.