The point on a fault at which first movement or break occurs during an earthquake is called the hypocenter or focus.

Here's why these terms are used:

* Hypocenter: This term literally means "below the center" and refers to the location within the Earth where the earthquake originates.

* Focus: This term emphasizes that the earthquake originates at a specific point within the Earth.

The epicenter is the point on the Earth's surface directly above the hypocenter. It's often the point where the strongest shaking is felt.