What is the origin of The Sign @ and does it have a proper name?
The Sign originated as a scribe's quick way of writing the Latin word ad especially in lists of prices of commodities.
It is usually known as The At Sign or The At Symbol which is good enough for most people. It is sometimes called Commercial A and occasionally by the French name arrobe or arroba. It has acquired various nicknames in other languages, but none has so far caught on in English.
As standardized Global English is spread by the media and the Internet, this sign became popular and widely used.