What is the official name for the # symbol coined by Bell Labs?

The official name for the # symbol coined by Bell Labs is octothorpe. Bell Telephone Laboratories engineers developed the term in the 1960s while working on touch-tone telephone keypads, which needed additional symbols alongside the digits.

“Octo-” is generally understood to refer to the symbol’s eight projecting points. The origin of “-thorpe” is less certain. One popular story connects it to Olympic athlete Jim Thorpe, while other Bell Labs accounts say the ending was invented as a playful, distinctive sound. The related spellings octothorp, octatherp, and octathorp also appear in historical sources.

Octothorpe is not the only name for #. Depending on context and region, people call it the hash sign, number sign, pound sign, or simply the hash key. “Hashtag” is a newer usage term for the symbol when it prefixes a word or phrase on social media. Thus, the quiz’s alternatives describe the character generally, while octothorpe is the Bell Labs coinage.