Today, the phrase “run amok” (also spelled “amuck”) is often used to describe such things as children making a mess while they run around and play. Classically, though, it more resembled the modern phrase “going postal” or someone who just snaps for various reasons and goes on a rampage.

One false etymology of run amok derives from sailors running a ship aground, literally running the ship into muck—but the English word most directly comes from the Malay amuck (also spelled amuk, and amuco), more or less meaning “attacking furiously” or “attacking with uncontrollable rage” or, more aptly, “homicidal mania.”

Some theorize this Malay word may have Indian origins or be from the name of a group of professional assassins in Malabar, called the Amuco. Others theorize that it came from the Malay word amar, meaning “fight,” specifically via Amar-khan, which was a certain type of warrior. Yet another theory is that the Malay amuck ultimately comes from the Sanskrit amokshya, meaning “that cannot be loosed.”

Whatever the case, amok first popped up in English around the 16th century, associated with the people of Malaysia and Java, first described in the 1516 text The Book of Duarte Barbosa: An Account of the Countries Bordering on the Indian Ocean and Their Inhabitants:

There are some of them [the Javanese] who go out into the streets, and kill as many persons as they meet. These are called Amuco.

The phrase “run amok” was partially popularized by Captain James Cook in 1772. From Cook’s book:

To run amock is to get drunk with opium… to sally forth from the house, kill the person or persons supposed to have injured the Amock, and any other person that attempts to impede his passage… indiscriminately killing and maiming villagers and animals in a frenzied attack.

In Malay culture at the time, some believed the state of amok was caused by an evil spirit, hantu belia, entering the body of a person, who would then run amok, attacking and attempting to kill anyone they came across, only to recover later and return to normal (if they weren’t killed first). Because it was thought an evil spirit caused this behavior, punishments for someone who ran amok and survived were typically light or even non-existent, with the person sometimes getting off scot-free. Usually, though, the person would be killed while running amok, and some speculate this was generally the point: Those who exhibited the behavior were often those who suddenly experienced great trauma in their lives and were looking for a way out. Sadly, this kind of thing can still be seen today.

Daven Hiskey runs the wildly popular interesting fact website Today I Found Out. To subscribe to his “Daily Knowledge” newsletter, click here.