Question

why did called 'reign of terror' of Robespierre government?

Answer 1

Because of his severe policies.
People believed that his government would help them getting rid of the 1st and 2nd estate people.But on the contrary he was a curse for them.
He made so dreadful policies for the people.

Answer 2

The Reign of Terror, or The Terror, is the label given by some historians to a period during the French Revolution after the First French Republic was established. Several historians consider the "reign of terror" to have begun in 1793, placing the starting date at either 5 September, June or March, while some consider it to have begun in September 1792, or even July 1789, but there is a consensus that it ended with the fall of Maximilien Robespierre in July 1794.