Mixed things. In recent (1900’s) popular culture it meant “at a rate of” in accounting and on invoices. It was not usually included on typewriters.
It is unique in that, unlike most (all?) other symbols, it does not have a formal name in English. Therefore, most language systems have come up with their own names (though many have adopted “at”).
It is worth mentioning that the earliest known acknowledgement of the symbol is in a Bulgarian translation of a Greek document dated as AD 1345. In this case, it is just acting as a capital “A”:
It is not known why this choice was made. There are several theories at the provided reference. It seems like it was not necessarily meant to be the same symbol that we are discussing now. In more recent (or, rather, less ancient) history, it was very often used to denote a specific measure of weight.
Apparently Spanish and Portuguese may also use it for gender-modification within the language:
The Spanish and Portuguese word amigos is an example of the @ being used for gender-inclusive purposes.. When the word represents not only male friends, but also female ones, the proponents of a gender-inclusive language replace it with amig@s.
Lastly, some of the interesting/funny/cute names for “@” in the enormous list at the given reference:
- “moon’s ear”
- “dog”, “doggy”, “dog’s head”
- “crazy A”
- “monkey”, “little monkey”, “monkey’s tail” (many languages that refer to monkey)
- “little mouse”
- “elephant’s trunk”
- “cat’s tail”
- “meow-meow” (Finnish; it sounds like this, I think; not actually sure how it should be pronounced)
- “cinnamon roll”
It has also been added to Morse code for the purpose of expressing email-addresses. This seems to be the only change to Morse code in one-hundred years.