Mental Floss

5 Quick Facts About the Hashtag

Jake Rossen
Technically it's called an octothorpe.
Technically it's called an octothorpe. / Nina Von Åkerman/EyeEm/Getty Images

The use of the hashtag as a Twitter tool to denote a specific topic in order for the masses to follow along—which was first suggested (in a Tweet, naturally) by Silicon Valley regular and early adopter Chris Messina—turned 15 years old in August 2022. Here’s a little history on its evolution from the humble numerical sign to the social media giant it is today.

1. The hashtag might come from the Latin term for “pound weight.”

There’s no definitive origin story for the hash (or pound) symbol, but one belief is that when people started to abbreviate the 14th-century Latin term for pound weight—libra pondo—to “lb,” they added a horizontal slash to denote that the letters were connected. (The bar was called a tittle.) As people began to write more quickly, the letters and the tittle became amalgamated, eventually morphing into the symbol we see today.

2. The hashtag should actually be called an octothorpe.

The symbol portion of the hashtag eventually made its way to dial-button telephones, the result of AT&T looking ahead to phones interacting with computers. In order to complete a square keypad with 10 digits (including 0), they added the numerical sign and an asterisk. AT&T employee Don MacPherson thought the sign needed a more official name, so he chose Octothorpeocto because it has eight points, and thorpe because he was a fan of football hero Jim Thorpe.

3. Twitter wasn’t big on the hashtag idea at first.

When web marketer Messina had the notion to add hashtags to keep track of conversations, he stopped by Twitter’s offices to make an informal pitch. He came at a bad time: Co-founder Biz Stone was trying to get the software back online after a crash and dismissed the idea with a “Sure, we’ll get right on that” burn. Undeterred, Messina started using them and the habit caught on.

4. The hashtag quickly spread beyond Twitter.

It wasn’t long before the hashtag took over Twitter: It began to be used to highlight interest in everything from political movements to breaking news stories; the frequency of hashtag use was (and is) often tied into popular culture. (Some of the most popular TV-related tags have been related to shows like #TheWalkingDead, and when it comes to movies, #StarWars has seen a lot of action.) Soon, the hashtag jumped to other social media platforms, including Instagram. While it was initially just a hyperlinked tagging system, the hashtag’s influence grew until, as some have argued, it changed the way we speak and communicate.

5. The hashtag is in the Oxford English Dictionary.

By 2014, respect for the hashtag had grown to the point where the venerable Oxford English Dictionary gave the word its stamp of approval. Their entry for the noun version of the word: “On social media websites and applications: a word or phrase preceded by a hash sign and used to identify messages relating to a specific topic. Also: a hash sign used in this way.”

A version of this story originally ran in 2017; it has been updated for 2022.