Teachable Moment

the Teachable Moment

What is an octothorpe?

Today, the octothorpe (#) or hashtag identifies movements, events, happenings, brands, etc., in digital searches. The symbol traces back to Ancient Rome. Romans used the Latin term Libra Pondo – lb, with a little bar across the tops of both letters (#) – meaning “pound measure” and handwritten, it also became the number sign. In chess, it represents a move that results in checkmate. In proofreading, it means insert a space. On Swedish maps, it represents a lumber yard. And it wound up on typewriter keyboards.

In 1963 the touch tone telephone was invented using buttons instead of a rotary dial. Bell Laboratories experimented with a few different designs for the telephone key pad, but ended up arranging the numbers 1 to 9 in a grid, and put zero alone at the bottom center.

In 1968, Bell decided to add keys on either side of the zero to make an even rectangle. So they chose the asterisk (*) and the pound sign (#), symbols that computers could recognize that were already on the standard keyboard. Bell Labs employees decided to call the # an “octothorpe” in their manuals. The hashtag was born in 2007 when Chris Messina used it for collating Twitter searches that could be input from a low-tech cell phone and sorted easily by a computer. Another Twitter user called it a “hashtag,” hash being the British term for the sign.

And that is how the octothorpe (or pound sign, or number sign, or hash mark, or hashtag) came into use on protest signs, billboards, promotional materials, in advertisements, TV shows, social movements, music videos, memes, and annoying conversations.