"Poltergeist" comes from the German words poltern, "to knock" and "rumbling spirit". The history of poltergeists can be traced as far back as ancient Roman times. Reports of poltergeist disturbances cite loud noises, lights, smells, physical and sexual assault, telephones ringing, and in general create unexplained disturbances. Some people believe that poltergeist activity is caused by an unconscious form of telekinesis.