Trepanning, also known as trepanation, trephination,  is a surgical interference in which a hole is drilled or scraped into the human skull, exposing the dura mater, to treat health problems related to intracranial diseases or release pressured blood buildup from an injury.

In ancient times, holes were drilled into a person who was behaving in what was considered an abnormal way to let out what people believed were evil spirits. Evidence of trepanation has been found in prehistoric human remains from Neolithic times onward. 

Maybe a method used by prehistoric people to evil spirits away