The word "amok" is an Indonesian word meaning "a murderous or violently uncontrollable frenzy".
The term dates back to the 1600s when it was observed among Indonesian natives. A person affected by an insane fit of rage would take the nearest weapon at hand, often a kris knife. He would then run into the streets and attack everyone in sight. Because these berzerkers would always fight to the death, many people would die before the killer could be subdued.
Some scholars believe this was a form of ritual suicide as it was often associated with serious personal problems.