When you discover something great on the Internet—a choice tweet or a Tumblr post that precisely reflects your mood—there are a few options for expressing how you feel. If the post is just alright, you might linger with the cursors above a favorite or reblog button, worrying about what message you'll be sending to your followers by giving it your imprimatur. But if something is truly great, you might find your fingers moving independently across the keyboard, tapping out "THIS."

Using This as an emphatic endorsement of whatever's onscreen is a piece of Internet slang so instinctual that each of us secretly believes we invented it. But the meme has a history.

The word emerged out of forum culture in the early 2000s, before the advent of mainstream social media. Online discussion forums had few of the trappings of Facebook or Twitter. Profile pages were rudimentary and there were no follower counts to brag about. The Like button didn't even exist. So how to express support of a great post without the potent symbol of a star or a heart to click on?

Writing "This." or "This^" (the caret points upward in the forum's chronologically-ordered conversation) may be the earliest form of a fav or reblog. It was web 1.0's quickest shorthand for liking something, reiterating it, owning the original poster's words as your own.

The phrase was defined by Urban Dictionary in 2007 as "an affirmation of the author's agreement with the quoted person's view or opinion." Fark.com, an online news discussion community founded in 1999, is cited as a source of the meme by Urban Dictionary user J. Harvey, and it's still visible there today. In a thread on gluten conspiracy theorists, poster Marcus Aurelius deploys "^ This ^ 2." (This, squared) in support of one particularly vitriolic rant. Another poster follows up with "Those^," effectively Thissing a This.

Like any good meme, not everyone gets it. A Yahoo Answers thread from 2009 asks what the word means and an unhelpful respondent suggests, "maybe they didn't finish what they were typing" [sic].

More recently, #This has emerged as a popular hashtag on Twitter and Tumblr. The meme appears everywhere, in images and GIFs starring Glee's Chris Colfer, ponies from My Little Pony, and Morgan Freeman—often with a hand gesturing upward replacing the earlier caret. "This." is even the name of an upcoming media venture from The Atlantic that promises to collect "highly recommended links to content."

Why is This so compelling online? Its etymology might provide a clue. The pronoun is a mixture of "the," which denotes a specific thing, and the Old English "seo," which is the imperative of the verb "to see." Put those together, and you get a command: See that. Look here. Sit up and pay attention. This creates context and specificity in the limitless Internet, where so many things demand our attention at once. We use This to mark something that deserves to stand out from the content stream.

Similarly, tagging something with This means we identify with it and it belongs to us. Such is the role #This plays on Twitter, where it's often found next to heartfelt aphorisms, reinforcing the site's innate pithiness. "Don't make a girl fall so d*mn hard if you don't plan catching her.. #ToBoys #This" tweets Baby Bear, a Filipino teenager. "Love doesn't need to be perfect, it just needs to be real. #this [a-ok hand emoji]" opines Hamad. My favorite is Roland Diaby, who tweets the Borgesian, "#this is my life." He lives the hashtag, which is paradoxically empty when it's not pointing at something.

On tumblr, however, #This reaches a fever pitch. It reveals a realm of humanity's most basic desires: emotional belonging, food, and lots of sex. The hashtag is affixed to inspirational messages like "Keep your head up high, beautiful" and "Skinny girls look good in clothes, fit girls look good naked," as well as batches of romantic black-and-white photos of couples making out. In one, an Abercrombie-ready young man lifts up his girlfriend, her legs twined around his waist as their lips meet. "THIS" is plastered on a black rectangle over the teenagers' torsos, as if the Tumblr user could inset themselves into the image through the writing alone.

In fact, the #This couple forms a mini-meme unto itself. It manifests in photos of a scruffy dude kissing a girl's neck, a swing-set makeout session, and snapshots of a very softcore bedroom session. The lust—not for sex as much as a stereotype of romance—is palpable.

#This expresses a range of intense desire, whether wholesome or fetishistic. It's used to tag furry porn and cartoons of Disney characters with ball gags as easily as a photo of an anonymous handsome dad leaning over a baby with "Coming home to this when I'm older," written across the image, a dream of wife- and motherhood (it was posted by Sara, a 21-year-old in Oregon). Moving beyond the "I like this" of forum culture, the meme has become shorthand for "I want this." A blog called Food Fuck illustrates this handily—it tags every food-porn photo it posts with #This, a verbal substitute for actually eating.

What ties the disparate strands of This together is their quality of aspiration. While a meme like #same is often used to reiterate a statement or a joke about current reality, This expresses an ideal future in which things might be different. The future is more confident, more fashionable, more romantic, full of more gently glistening salads than the present.

These days, we have likes and favorites and reblogs to show that we agree with our friends online. Instead of aging into irrelevance, though, This has evolved into something altogether different from its forum origins. We use it like an inflatable lifesaver in the anonymous expanse of the Internet to represent a sense hope and belonging. It's a tool that everyone owns, no matter who made it up first.

With a history stretching back over a decade, This has already survived far longer than many Internet memes; perhaps that's why it feels a little dated as far as Web vocabulary. Yet a meme by definition is a unit of communication, and the function of This is to help us communicate better by creating specificity—it's a meme's meme. As a natural part of language, This has more utility and a longer shelf life than a finite joke meme like Grumpy Cat or Doge. It will be there for us as long as we need it.

Perhaps the message is best summed up in one image found on Tumblr's #This: "Dear whoever is reading this: you're beautiful and someone out there is crazy about you. So smile. Life is too short to be unhappy."