#barcamp is the first hashtag ever used. It was posted by Chris Messina in a Tweet which read: ‘how do you feel about using # (pound) for groups. As in #barcamp [msg]? on 23 Aug 2007. To be precise, this was the first time a word or phrase preceded by a # sign was used in a way that we today describe as a hashtag. The term ‘hashtag’ only came to the existence 3 days later. It was first used by Stowe Boyd on 26 August 2007 in his blog post “Hash Tags = Twitter Groupings”.
Hashtag is a relatively new word. It was first used in 2007 as a simple user based innovation (#barcamp) useful for the organisation of content on Twitter. Since then it has enjoyed a rapid spread (#sandiegofire) on Twitter, across other social media and far beyond. In 2010 ‘Trending topics’ were introduced on Twitter based on the most popular hashtags. In 2012 ‘Hashtag’ was selected as the Word of the Year by The American Dialect Society.