What Common Symbol Is Technically Known as an “Octothorpe”?

Most people see the # symbol multiple times every day – especially if you’re an avid social media user. It’s on your keyboard and on your telephone keypad. Depending on where you live (and perhaps your age), you might refer to this little symbol as a number sign, pound sign, hash, or hashtag. But did you know that it’s also known as an “octothorpe”?

The number sign has a somewhat confusing history, with its origins dating back to an abbreviation of the libra pondo ("pound weight") symbol. Yet by the mid-19th century, it had come to resemble the symbol we know today and gained its current meaning as a number sign. It was included on the Remington typewriter in the 1880s and later in teleprinters and ASCII codes before making its way onto computer keyboards.

It’s widely known as the “pound” or “pound sign” in the United States, though “number sign” is more common in certain regions, as well as in Canada. In many other countries, it’s the “hash.” However, thanks to its widespread use for metadata on sites like Twitter and Instagram, the term “hashtag” has become increasingly popular, especially for people who have grown up with social media. When used in front of a keyword, it helps to identify posts relating to a particular topic.

So where does “octothorpe” (or “octothorp”) come in? Most scholars agree that the term was devised by engineers at Bell Telephone Laboratories in the 1960s, when the symbol was added, along with the asterisk, to telephone keypads. The symbol has eight points, which explains the “octo.” Theories abound to explain the rest of the name. One common story is that it was simply a joke word originally spelled “octotherp.”

Some say it was based on “burp,” which is what one Bell Labs employee did while talking about it. Or it could relate to Olympic athlete Jim Thorpe or even James Oglethorpe, founder of colonial Georgia. Another idea is that it was based on the Old English word “thorp,” meaning village, as it looks a bit like a village surrounded by eight fields.

The oddity of the octothorpe: