A versatile symbol with many names (among them hash mark, number sign, and pound sign), the octothorpe has become popularized in hashtags, those words or phrases prefixed by the symbol on Twitter and other social media especially to classify or categorize the accompanying text. The octothorpe is believed to have been adopted by the telecommunications industry with the advent of touch-tone dialing in the 1960s, but it remains unknown how, exactly, the symbol got its odd name. The octo- part almost certainly refers to the eight points on the symbol, but the -thorpe bit is mysterious. One story links it to a telephone company employee who happened to burp while talking about the symbol with coworkers. Another relates it to the athlete Jim Thorpe and the campaign to restore posthumously his Olympic medals, which were taken away after it was discovered that he played baseball professionally previous to the 1912 Games. A third claims it derives from an Old English word for “village.”

Examples

“… Messina chose to use this symbol for collating Twitter searches in 2007 because he wanted a sign that could be input from a low-tech cellphone. He had two options: octothorpe or asterisk. He chose the former.” — Roman Mars, Slate.com, 17 Dec. 2014

“Shady Characters explores the history of this and many other non-mainstream punctuation marks, such as the interrobang, the octothorpe (that’s the hash symbol), … and the ampersand.” — Brandon Robshaw, The Independent (UK), 21 Feb. 2015