The song Stan, released in 2000 by Eminem, tells the story of his imaginary "biggest fan", who is so obsessed with the singer that he can't stand being ignored by him, becomes violent towards his girlfriend, and eventually commits a murder-suicide.

Inspired by the song, the word "stan" took a life of its own, as a way to qualify people who are particularly overzealous in their defense of a celebrity, a media, or anything else. Even though it usually has a negative connotation, there are some people who enjoy calling themselves stans of a celebrity or a fandom.

It can also be used as a verb, to call someone out for being blindly defensive of something. This is why you might sometimes see people being asked to "stop stanning for X", implying that they are purposefully refusing to acknowledge the negative aspects of a person, media, or something else.

Although it is sometimes claimed the name "stan" is a combination of the words "stalker" and "fan", nothing proves (or disproves) that it was purposefully picked by Eminem for this specific reason.