I know # is “hashtag” nowadays, but I read somewhere recently, and now can’t get it out of my head, every time I see this...
# used to be called “pound” back in the day...
#metoo?
I always called it "pound" and still do, but I had a math teacher who always referred to it as the "sharp" symbol, as in music. He said it was the "sharp" symbol long before it was the "pound" symbol.