According to Wikipedia, a hashtag is a metadata tag that is prefaced by the hash symbol “#”, Hashtags are widely used as a form of user-generated tagging that enables cross-referencing of content sharing a subject or theme. But the hash also has other functions. I embarked on some research.

The hash symbol has many different names in different countries and languages. In Switzerland it’s known as the Gartenhag, Doppelkreuz, Raute, Schweinegatter or Lattenkreuz. In English-speaking countries it can also be referred to as the pound sign or number sign – the latter when it’s placed in front of a figure to indicate an ordinal number (a practice that isn’t so common in Switzerland).

The hash in music

Anyone with a grounding in music theory, indeed anyone who’s ever learned the recorder, is familiar with the sharp sign. Although it’s slightly different in appearance from the classic hash symbol, it’s very closely related. When placed directly after a note, it raises its pitch by a semitone, for example making a F into F sharp or a G into G sharp. If the sharp sign is at the beginning of the line right next to the clef, it’s an indication that the note in question should be played as a sharp all the way through the piece, unless instructed otherwise. The number of sharp signs by the clef also shows what key signature the music is written in (for example G major or D major). In musical notation there’s also a flat symbol (♭), which does something similar that we won’t go into here.

The hash in programming

In IT and computing the hash is also an important element in programming languages. Among other things, it serves as an indicator for comments, is placed in front of colour information or, if you enter it in the search bar, leads back to the main page in many directories (bet you didn’t know that!). As we see, this much-used sign plays an important role in simplifying matters in a variety of technical languages, from music to IT. In each case it serves as a means of orientation – which also applies to the way it’s now combined with keywords on the internet as a hashtag.

Origins in antiquity

The origins of the hash symbol go back to Roman times and the term libra pondo, which translates as “pound weight”. This is still reflected in the use of the pound sign (a hash) in English. In the Middle Ages the words libra pondo were replaced with a lowercase l and p with a horizontal line across (at the time standard practice for abbreviations). It’s said that owing to its frequent use in business ledgers and related documents, a certain carelessness gradually crept in, and two small letters and the line were simplified to the symbol now known as the pound sign. The hash was born.

The hash(tag) today

The hashtag – the combination of a hash and a keyword – was born on 23 August 2007, around a year after the launch of Twitter. This was the start of a success story: the combination of symbol and word to make linking and finding search terms on the internet easier. So we have Twitter to blame. It wasn’t until several years later that other social media channels such as Google+ (2011) and Facebook (2013) jumped on the bandwagon and started making the hashtag system available to their users as well. Today it’s hard to imagine social media without it.

The hashtag #JeSuisCharlie is a good, if tragic, example of a successful hashtag: the hashtag, which went around the globe to demonstrate solidarity following the attacks on the French satirical magazine Charlie Hebdo, was used a total of almost seven (7!) million times to mark posts accordingly. This is an impressive number that continues to be a model for subsequent solidarity hashtags (#WeAreOrlando, #WeAreParis, etc.). Incidentally, Hash is also a first and last name, although its use as a first name is fairly rare. Why anyone would call their child Hash is also a good question. But that’s another story.

My three favourite hashtags of the moment
#newwork #digitalisierung #EheFuerAlle