Trepanning, also known as trepanation, trephination, trephining or making a burr hole is a surgical intervention in which a hole is drilled or scraped into the human skull.

What Trephination means?

: an act or instance of perforating the skull with a surgical instrument.

Why was Trephination done?

In ancient times, trepanation was thought to be a treatment for various ailments, such as head injuries. It may also have been used to treat pain. Some scientists also think that the practice was used to pull spirits from the body in rituals. Many times, the person would survive and heal after the surgery.