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A short, sourced series

The history of the # symbol and the hashtag

The # symbol is far older than the hashtag — older than computers, older than the telephone. This series digs up where it actually came from and follows it all the way to the tag you use today. Read it in order, or start anywhere; every chapter loops to the next.

The history of the # symbol and the hashtag
  1. 1The whole storyThe history of the hashtag: from a Roman pound to a global symbolThe # symbol is older than computers by centuries. The full history of the hashtag — from a Roman unit of weight, through the octothorpe, to the social movements it powered.
  2. 2Chapter 1 — the originWhere the # symbol came from: a Roman pound, abbreviatedThe # symbol comes from the Latin “libra pondo” (a pound by weight). Scribes abbreviated it “lb” with a bar, and centuries of rushed handwriting turned it into #.
  3. 3Chapter 2 — the strange nameThe octothorpe: how the telephone gave # a new nameWhen Bell Labs added # to the touch-tone phone keypad in the late 1960s, engineers coined a deliberately odd name for it: the octothorpe. Here is the disputed story.
  4. 4Chapter 3 — the namesPound, number, hash, sharp: the many names of #Pound sign, number sign, hash, octothorpe, and the lookalike musical sharp — the # symbol answers to more names than almost any other character. Where each one comes from.
  5. 5Chapter 4 — the digital lifeFrom code to chat: the # symbol in computingLong before the hashtag, # was everywhere in computing — the C preprocessor, the shebang line, comments, IRC channels, URL anchors, hex colours, and Markdown headings.
  6. 6Chapter 5 — the inventionWho invented the hashtag? Chris Messina and a 2007 tweetThe hashtag was proposed by Chris Messina on Twitter on 23 August 2007. Twitter was lukewarm; the 2007 wildfires proved it, the word stuck, and movements made it global.

Prefer the practical version? What is a #hashtag? explains how hashtags work today — and how you can own one as a #Name.