Octothorp, weird yet interesting word isn’t it?
Maybe you’ve seen it in any of these other traditional spellings: octalthorpe / octothorp / octothorpe / octatherp
It’s just one word used to represent that symbol at top, you’re probably most familiar with it as part of the telephone number pad. In most regions of the US and Canada it’s more often called the ‘pound sign’ or the ‘number sign’.
Little is known about this word, but two things we do know. One is that this is truly an obscure word, to the point where most dictionaries don’t even list it, including the Oxford English Dictionary. Second thing known for sure is that the etymology of this word is definitely obscure.
There are a lot of stories that try to explain how it got its name and the experts can’t really agree on the true story. The first part of the name is not in question, ‘Octo-‘, which is Latin for eight because of the eight points on the symbol. But the second half of the name ‘thorp’ is in doubt, if you’d like to read the various stories of explanation then you should check out the article here on worldwidewords.org and this explanation by Octothorp Press on their ‘About the Octothorp‘ page.