A Brief History of the Hashtag, and Other Unusual Punctuation Marks
The New YorkerTwitter might have popularised it, but the hashtag is a lot older. It dates back to the 14th century and evolved from the abbreviation for a pound, lb.
From Weekly Filet #128, in August 2014.
💔 Some older links might be broken — that's the state of the web, sadly. If you find one, ping me.