The word “die” has the same number of letters. Written in isolation, “die” immediately feels like a powerful, hateful word. But “kys”, usually styled with every letter in lower case, has none of these connotations.

With its resemblance to “kiss”, it looks almost sweet. Yet it has the same meaning as “die”. Kys is an instruction. It means, quite simply, “kill yourself”.

Or does it? These are the words that the initialism has stood for since 2003, when it was first defined on the Urban Dictionary website, the home of online slang. Yet, as perverse as it may seem, the word originated as a joke among friends.

When someone made an ignorant remark online, they would be dismissed with the three little letters. A Facebook user once complained that a teacher had told her son that he was a “Homo sapien” (confusing the term with “homosexual”), and the internet’s response was simple: “Please, kill yourself.”

“Kys” is favoured by children and teens, most of whom argue that it’s just a joke. Regardless, it seems remarkable that we now have a commonly used shorthand to provoke suicide. Cyber-psychologists often speak of the “online disinhibition effect” – our tendency to say things on the internet that we would never dare to say in real life.

This month, the Crown Prosecution Service (CPS) announced that online hate crime will be treated as seriously as offline offences. Yet the welcome move leaves questions unanswered. Just over a year ago, the Labour MP Thangam Debbonaire was widely mocked for reporting a student who had told her to “get in the sea”, a popular phrase used to signal disdain.

What’s in a name? A death threat by any other name is a crime to tweet. The CPS may therefore have great difficulty drawing the line between acceptable online jokes and authentic threats. Though many view “kys” as funny, it can cause genuine distress.

As awareness of mental health issues increases, many youngsters are urging others to stop using the word. Some agree. Others have a handy three-letter reply.