Pound, Number sign or Hashtag

What’s the origin of the hashtag  # symbol?

Well, right off we need to note that it has be known by several names: the pound sign, the number sign, the octothorpe and the hashtag. 

Though the hashtag usage is recent, it also has an origin going back to ancient Rome.

As a hashtag, it precedes a word or phrase to clarify or categorize the accompanying text. It came into wide use in the past decade via social networks, especially on Twitter. Looking at the Twitter home page, you can see the currently trending (popular) hashtags. People can follow hashtags to see what content has been posted about the subject, such as #DonaldTrump or #ClimateChange, and follow online trends.

The first use of the pound sign on Twitter was:

How do you feel about using # (pound) for groups. As in #barcamp [msg]? 

by Chris Messina ("factoryjoe") on August 23, 2007.



The possible ancient origin is to the symbol ℔, an abbreviation of the Roman term libra pondo, which translates as "pound weight." Ultimately, the symbol was reduced for clarity as an overlay of two horizontal strokes "=" across two slash-like strokes "//".

The symbol is described as the "number" character in an 1853 treatise on bookkeeping. It seems to have been used primarily in handwritten materials. In the printing business, the numero (№) symbol and barred-lb (℔) are used for "number" and "pounds" respectively. It appeared on the keyboard of the Remington Standard typewriter in 1886.

To confuse our international readers, the US pound sign, number sign or hash symbol "#" is often used in information technology to highlight a special meaning. But "Pound sign" in the UK means "£"  and is used for money, while "#" is called hash, gate, and occasionally octothorpe.

The symbol is also used in several ways in computer coding.

The graphically similar symbol of the sharp (♯) is used in musical nomenclature. Also similar is the the equal-and-parallel symbol (⋕) from mathematics, though both of these are distinguished by its combination of level horizontal strokes and right-tilting vertical strokes.