A History of the Octothorpe, A.K.A the Pound Sign or Hash


The octothorpe is one of the most commonly-used symbols in the western world, thanks to the introduction of the hashtag concept on Twitter (#thanksTwitter). The symbol continues to signify a number of different things in the world beyond twitter hashtags, including acting as shorthand for the word “number” or “pound” (as in weight). But where did this symbol come from and what did it originally mean?

Somehow lb Became #

Surprisingly, the pound sign/octothorpe does not have the same storied history of use that other conventional punctuation marks have, such as the period or question mark. Some of the earliest known uses of the symbol date back from traders’ logs in southern Europe in the 17th century, where they used a funky version of the symbol as shorthand for the word pound, as in weight. Historians surmise that the hashtag was borne from a very messy scrawling of ℔, which stood for weight in pounds (fun fact: lb stands for libra pondo – Italian for weight in pounds). When traders and bookkeepers would hastily write ℔ in their records in cursive, it’d end up looking like the letters had been crossed out not once, but twice.

19th century bookkeepers’ manuals note that the pound/hashtag symbol stood for pounds, just as it had been used centuries before. Still, at that point the symbol was only used in handwriting and was not a part of standard printing type. Around the same time, the symbol also was used to stand for the word “number” as in #1, #2, etc. The typewriter became commercially available in the late 1800’s and by around 1910, keyboard layouts became more standardized. Most keyboards around the turn of the twentieth century included the pound symbol in their keyboard layout, which propelled its popularity and use to even greater heights.

The pound sign then gained another meaning after the invention of the touch tone phone in 1963. Since the numbers no longer needed to be arranged in a circular shape as they did on rotary phones, telephone engineers at Bell Labs had to determine a new layout for the number buttons. Wanting to create an even three by four rectangle, the engineers added two extra buttons: the asterisk (*) and pound sign (#). These additional buttons could allow people to take greater advantage of new features that touch tone phones provided, such as automated menus.

From Typewriters to Telephones

Since the pound sign did not have an official name at this point, the Bell Labs engineers decided to formally name it themselves. They came up with octothorpe: “octo” to represent the 8 lines that come off of the sides and “thorpe” as a tribute to olympic athlete Jim Thorpe (according to rumor and urban legend, at least). The symbol was official known as the octothorpe after that moment… until the advent of the Twitter hashtag, of course.

The octothorpe/pound sign received a huge boost in popularity and usage after it became a way to categorize posts on popular microblogging website, Twitter. Twitter user and software developer Chris Messina was the first to suggest using the octothorpe to tag posts and categorize them back in 2007. Doing so would allow users to easily categorize their own posts and search for others like it. The use of the pound sign to denote a post’s hashtag/category became immensely popular in the following two years, especially when users were discussing particularly tumultuous events such as the 2007 San Diego forest fires and the 2009 Iranian election protests. The popularity of hashtagging spread to other social media outlets, including Instagram and Facebook.

Twitter and Beyond

Though the number sign/pound sign/octothorpe is very popular for its use as a social media hashtag these days, the symbol has also been used heavily in computer coding and in musical notation over the past century. Since the symbol is now standard on practically every computer and smartphone keyboard, chances are that the symbol will only gain more applications over time. #TheEnd