trephining refers to the process of a. making a person chant and pray to drive out evil spirits b. changing one's diet to improve one's physical and mental health c. boring a hole in the skull to let evil spirits escape d. putting leaches on the body to remove bad blood

Trephining refers to the process of "boring a hole in the skull to let evil spirits escape".

Trephining refers to a careful mediation in which a hole is penetrated or scratched into the human skull, uncovering the dura mater to treat medical issues identified with intracranial infections or discharge constrained blood development from damage. It might likewise allude to any "burr" hole made through other body surfaces, including nail beds. Usually used to mitigate weight underneath a surface. A trephine is an instrument utilized for removing a round bit of skull bone.  

In ancient times, holes were penetrated into a man who was carrying on in what was viewed as an unusual method to let out what individuals accepted were evil spirits.