Stan is a rare thing: a slang word with an exact birthday. On 20 November 2000, Eminem released "Stan", a single from The Marshall Mathers LP featuring Dido. It tells the story of an obsessive fan whose letters grow more desperate as his devotion turns dangerous. The fan's name became the word.

At first it was an insult. Dictionary.com notes that in 2001 Nas used "stan" in a track as a put-down for obsessed fans, and the word kept that edge for years. But fan communities do something interesting with insults: they adopt them. By 2008, Dictionary.com finds, people on Twitter were using "stan" as a verb of admiration, and through the 2010s whole online communities called themselves stans.

Dictionaries followed. In 2017 Time reported it as the Oxford English Dictionary's latest addition, defined as "an overzealous or obsessive fan of a particular celebrity", with a verb sense too. Merriam-Webster added it to its online dictionary in 2019.

You'll often hear that stan blends "stalker" and "fan". It's a neat theory, but Wikipedia reports Eminem's manager explaining that the name was chosen simply because it rhymed with "fan". The coincidence probably helped the word catch on. Today "we stan" is mostly affectionate. The word comes from a song that warns about fandom going too far, which is easy to forget.