Hash. Pound. Number. Octothorpe. Grid. Crunch. Diamond. Sharp. Mesh. Crosshatch. Thud. Thump. Splat. Scratchmark. Square. Hex. Flash. Tic-tac-toe. Pig-pen.

The host of names the “#” symbol has had over the centuries only just outnumbers the plethora of functions it has fulfilled. From when the Latin for “pound” began being written as “lb” (short for libra) with a line through the top, to the creation of millions of hashtags a day on Twitter, it has had a colourful history.

It was once a humble little character, perching unused on telephone keypads, merely called upon when enraged diallers had to speak to dismissive machines on the other end, and is relegated on most Mac keyboards to only being conjured up by hitting Alt+3. But then the arrival of Twitter saw it being typed, tapped and clicked into prominence – a symbol to lead all symbols. A globally lauded criss-cross of breaking news, campaigns, and digitally-delivered jokes.

Here’s its story.

Latin roots

Finding out when the hash symbol was first used would require a “pretty much character-by-character hunt of seventeenth and eighteenth-century books to find it,” according to Shady Characters author and blogger Keith Houston.

But we know its roots are in the Romans’ use of the term libra pondo, meaning “pound in weight”. This was eventually shortened to “lb” for libra, and when English speakers began writing this abbreviation, they put a little line across the top to indicate the contraction.

“As people wrote this faster and faster, it just evolved into the hash symbol,” Houston, who has investigated the character’s evolution, explains.

In the late seventeenth century, Isaac Newton was writing the “lb” contraction, and English printers had made it an official character by having it preserved in lead as a symbol to be used in printing. But precisely when writers became careless enough to scribble it as “#” is unclear. It was at some point after the late seventeenth century and before the nineteenth century. In the US, it is still often referred to as the pound sign.

Shebang!

Other than the pound sign, it is also known as a number sign, mainly in America. In the UK, we call it hash (from “cross-hatch”), but it has a wealth of other, more fun, names, including crunch, diamond, flash, tic-tac-toe and pig-pen.

“This is one of the problems,” laments Houston of the symbol’s convoluted history. “It has so many names.”

It's been a very versatile symbol, being used to indicate numbers, weight, checkmate, a sharp musical note, spaces between words by proofreaders, the end of press releases (when written in a trio), and, today, hashtags.

It also has an alternative, edgier identity when coupled with an exclamation mark: “shebang” (the rather beautiful “#!”). This is also known by the equally satisfying “hashbang”. It’s a programming symbol used by the UNIX operating system (which forms the basis of Linux, Android and others).

Yet its most obscure incarnation must be its label as the “octothorpe”.

The name octothorpe came about when hash hit the phones. It’s often thought that the hash key began its life in the undignified role as a function for signifying numbers over the phone on automated customer service systems. But it already existed on Qwerty typewriter keyboards before it reached telephone keypads.

An American invention, the Qwerty design reached keyboards in the 1870s. Houston points out that “the use of it [#] as a number symbol was quite common. So it was important enough to make its way onto the typewriter.”

Yet it was mainly used by “the sort of people who were using typewriters, business people”, rather than the general public. This was along with its brother-in-resurgence “@”, which was, back then, used humbly as an abbreviation for “at the rate of” – before it became the spiralled backbone of email.

“The keyboard that you have – and the one I'm looking at at the moment on my laptop ­­­– is effectively a bit of a relic,” Houston enthuses. “It has some new keys on it, but it's remained largely unchanged for a good, what, I'm thinking, 150 years or so. A bit less than that, maybe. No one had ever stopped printing hash marks. So it was there, it was recognised, but just not as especially well-used amongst the great mass of people.”

And it was the touch-tone telephone that brought the hash key to the grubby fingers of the public. Along with its fellow traveller, the asterisk, hash was added in 1968 to the push-button telephone keypad, which was created at Bell Labs (a historic laboratory in the US named after Alexander Graham Bell) in the 1950s.

Pissing off Germans

It was also at Bell Labs where the hash symbol was christened the octothorpe. But this quirky moniker has so many explanations, its story has almost descended into myth.

“Two or three different people have claimed to have created it,” Houston reveals. “I find this amazing. I've talked to one of the guys who says he invented it, and I've talked to another guy who said he popularised it.”

The first theory is that some Bell Labs employees wanted to “piss off” international users by inventing a name that is difficult to say in some languages.

“The guy who had to come up with names was very big on picking something within an international standard... his co-workers thought this was ridiculous: ‘we're an American company, why do we care?’ So they invented a name with a ‘th’, which they thought the Germans would have trouble with, for example”, laughs Houston.

Another possible derivation is the name Oglethorpe, after James Oglethorpe, the British general who founded the US state of Georgia, plus “octo” for eight – the number of legs in the hash sign. But this explanation has only appeared in one dictionary.

The OED proffers the story that fans of native American athlete Jim Thorpe – who was stripped of his Olympic medals due to ineligibility for having done a stint in professional basketball – at Bell Labs named the symbol after him.

Then there’s the idea of “thorpe” being an old Norse word for village or town (eg. Scunthorpe), and the criss-cross pattern of the hash sign suggesting a plot of eight fields surrounding a village. But, as Houston points out, “you're talking about ‘thorpe’ which comes from Norse, and ‘octo’ is Greek, so it's maybe a bit of a reach to imagine that it sort of came out of nowhere rather than naturally formed that way, so there's no proof of that.”

A visual reminder of equality

So once the octothorpe, which no one outside of computing or telecoms knew was called the octothorpe, was a fully-fledged button and key, it stayed that way. Never quite superfluous, but also a bit of a mystery, it sat forever at the tips of our fingers, rarely being deployed.

“It doesn't feel like it was in decline,” Houston observes, “[but] it certainly felt like it was always just sort of pottering along under the radar. It didn't have a single kind of starring role in anything.”

I ask Robert Fulford, Canadian journalist, author and symbol obsessive, about the enduring allure of the symbol.

“Who wants to see these beloved symbols, these things that have served us so well, who wants to see them forgotten?” he asks. "There's this competitive thing going on there, between symbols. Like blue jeans have wiped out most of the market for certain types of pants, in the same way there'll be various symbols that get wiped out, or set aside."

He is talking to me enthusiastically over the phone from Toronto, and seems genuinely grateful that I am apparently “only one of the two people in the world” to have asked him about the subject he holds so dear, but admits caring about symbols is a “bizarre” interest.

“I just imagine these things having a personality or pride, you know?” he tells me.

For Fulford, the hash symbol's personality is one of equality:

“The octothorpe is beautiful! It's beautiful!” he cries. “It's the very definition of orderliness, and it has a pattern that seems to suggest, as some people have noticed, a city square or a piece of property, divided into equal parts. It's a wonderful picture of equivalence; everything is equal.

“It's kind of an old-fashioned communist thing – I don't think communists used it, but it has that ‘equality for everyone’ perception. And as we know, inequality has become the great problem of the last 18 months or so, and that is a visual reminder of equality.”

"For nerds"

Perhaps this zeitgeisty aspect pointed out by Fulford was a factor in the hash finding its celebrity status. Its use as a hashtag on Twitter has brought the unassuming little pattern worldwide acclaim. It has crawled out on eight legs from numerical obscurity to a world of flashy 24-hour media attention. And it’s consistently trending.

However, it almost never embarked on its Twitter career.

Inventor of the hashtag and self-proclaimed “typography lover” Chris Messina reveals that, when he mooted it in 2007, with a tweet (below), it wasn’t popular with the Twitter gods.

how do you feel about using # (pound) for groups. As in #barcamp [msg]? — Chris Messina™ (@chrismessina) August 23, 2007

“They didn't like it,” Messina recalls. “They said it was ‘for nerds’ and would likely never catch on. Twitter eventually acquired several companies and apps (Tweetie and Summize in particular – a Mac app and Twitter search engine respectively) that had already supported hashtags. The more companies they acquired that supported hashtags, the more inevitable it became that Twitter would need to officially support them.”

Messina, who didn’t work at Twitter but was in development at Google at the time, explains why he felt Twitter needed a hashtag type function at all:

“I wanted to offer a simple way for the Twitter community to organize itself. Twitter didn’t support groups, so I figured the next best thing to do was to use the text of a tweet to indicate topicality.”

But why choose the hash sign, or pound, as he called it? The reason is rather less mysterious than the character’s history. It was “easy to type on feature phones”, according to Messina, and had also been used previously on early internet chat channels to signify a name of a chat room. “It seemed to me that appropriating something that was already used elsewhere would increase its chances of adoption,” he muses, “rather than inventing something completely new.”

And he was right. But it wasn’t just a pragmatic choice. Messina expresses a genuine love for the symbol.

“Of all the possible symbols I could have chosen, I think the octothorpe was the best one I could have picked,” he says. “As a typography lover, I do like the look of the symbol. It's one of the more dense characters, so you can see it from a distance or at a glance – it's hard to miss!

“I guess I've come to really identify with the symbol – it's quirky and a bit underrated but had something to offer that perhaps it itself hadn't even realized before. I can relate to that.”

And so, it seems, can 255 million tweeters. #History.