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The # symbol is officially called an octothorpe

Some trivia is so bizarre it forces you to rethink your entire understanding of the world. Check out the fact below, see how others reacted, and scroll down to dive into the verified science and history behind it.

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The symbol # is officially named the 'octothorpe'. The 'octo' refers to its eight points. The 'thorpe' is disputed — possibly after an obscure word for 'village', possibly after a joke by engineers at Bell Laboratories in the 1960s who named it after Jim Thorpe (the athlete) while working on telephone keypads. It has also been called a 'pound sign' (from the abbreviation for pounds weight, Lb), a 'number sign', a 'hash', and a 'sharp' in music notation. Twitter's use in 2007 transformed it into the 'hashtag'.

Why this is surprising

A symbol seen billions of times per day as a hashtag has a strange and disputed proper name. The gap between how universal the symbol is and how unknown its official name remains is a quiet measure of how much language floats free of its labels.

The Science Behind It

OddlyHuman EditorsJune 2026

The symbol # is officially named the 'octothorpe'. The 'octo' refers to its eight points. The 'thorpe' is disputed — possibly after an obscure word for 'village', possibly after a joke by engineers at Bell Laboratories in the 1960s who named it after Jim Thorpe (the athlete) while working on telephone keypads. It has also been called a 'pound sign' (from the abbreviation for pounds weight, Lb), a 'number sign', a 'hash', and a 'sharp' in music notation. Twitter's use in 2007 transformed it into the 'hashtag'.

Why Your Brain Finds This Hard to Believe

OddlyHuman Editors

Verified

Written and fact-checked by the OddlyHuman Behavioral Science Team. We verify all psychological, sociological, and historical claims against peer-reviewed journals, primary sources, and established encyclopedias to bring you accurate insights.

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The # symbol is officially called an octothorpe. The name may have been invented as a joke by Bell Labs engineers in the 1960s. Before Twitter, most people called it a pound sign. #OddlyHuman