Question

Why Jacobin were known as sans culottes

Answer 1

during french revolution, the dress of jacobin club were trousers without knee breaches and a red cap.

in French, sans culottes meant those without knee breaches. So, Jacobin were known as sans culottes

Answer 2

The sans-culottes (French: [sɑ̃kylɔt], literally "without breeches") were the common people of the lower classes in late 18th century France, a great many of whom became radical and militant partisans of the French Revolution in response to their poor quality of life under the Ancien Régime.