Octothorpe for life.

The symbol # is a “hash”. The “tag” Is the word that follows.

The hash exists as a signal to a computer program indexing posts by topic that the following characters before the next whitespace are meant to signify a tagging of a topic. Twitter started doing this a long time ago, to give users a way to categorize their posts by topic without needing a separate interface. (Did you know that the original 140 character tweet length was so it could fit in a single SMS message? Twitter used to be operable over text message). It’s likely that the # symbol was chosen because in URLs it’s used to signify a page anchor in HTML documents, such as a specific header or paragraph, and so similarly here it’s used to find specific topics; you’re anchoring your interest to something specific.

So it’s not a “hashtag” without the hash and the tag. #TIL

IIRC Twitter introduced using # to make words searchable across all of the tweets, hence the name.

I grew up with # being pound as well. The use of the pound symbol to highlight shit came from coding. Hash is another word for the pound symbol. It tags stuff. Ergo hashtag. Born in the glory years of Twitter.

What are you talking about, the octothorpe?

https://snomoto.com/the-octothorpe-why-we-stopped-calling-it-a-hashtag-and-why-it-matters-1bol

You just wanted to say 'pound Taylor Swift', didn't you?

I always called it the number sign.

To expand on what others are saying.

Hash is one of the many names for #. Twitter and other platforms allowed you to use hash to tag your posts with a searchable keyword. Hence "hash tag" which gets shortened to hashtag.

People on these platforms may have had cause to use and think about # on a much larger scale than would've been common at that time. Sure you may be asked to press pound on a phonecall once in a while, but that never happened often enough that I could fully keep it straight from star. It was usually just stored in my head as "the special phone key that isn't star"

I think it was always called a hash but we read it as pound or number...7# or #7. Like how we say 'and' instead of saying ampersand.

https://en.wikipedia.org/wiki/Hashtag#Origin_and_acceptance

I still remember, in the late 2000s and early 2010s, finding that somewhat weird too. I was already regularly using the Internet (including forums) well before hashtags were invented and when I started to see hashtags in all kinds of contexts, I on the one hand found it great that the Internet was apparently arriving in more people's lives, and on the other hand somewhat disappointing that they weren't using forums or wikis or anything like that that I was already highly familiar with, but this weird new thing called Twitter... oh well...

On a Touch Tone phone, this is called the Pound Sign (US).

Contemporary to hashtags being invented on Twitter was the use of tags to categorize blog posts. See https://en.wikipedia.org/wiki/Folksonomy

Also, note that hashtags on Twitter started as a grassroots convention before it was supported as an official feature.

It was pound sign to me and the first time I heard hashtag was people describing twitter things which I never got into.

Remember the #MeToo movement? Now read that out loud, but use "pound" instead.

It’s a sh, as in #!/

In France it was "dièse" (like "sharp" in music) and it became hashtag too. In Québec it's the "carré" meaning the square, and people says hashtag now too.

There may not be stupid questions, but this thread proves that there are certainly stupid answers.

The term was popularized with Twitter but tags for search purposes etc had been a thing for a long time before then.

Funny how # is used in some programming/scripting languages to ignore stuff…but on twitter to pay attention to stuff

When I was a kid, the * key was "squishbug". Why did that change

The world (or at least the Anglosphere) has always called the # symbol the hash sign. I have no idea why Americans called it the pound sign - most places call the £ symbol the pound sign.

The term "hashtag" was not invented by an American. For the rest of us this makes sense - it's a tag denoted by a hash sign - but I can see how it seemingly came out of nowhere if you used different words.

This was a joke question. The definition of "pound" as used in the context of OP's question is newer than the definition of "#" as "hash".