Where did the At Sign come from?

The "@" symbol, also known as the at sign, has a history rooted in commerce and accounting. It was originally used by merchants in accounting to represent "at the rate of" on invoices and ledgers. Its modern use in email addresses and social media can be traced back to the early days of the internet, chosen by Ray Tomlinson in 1971 to separate the user's name from their host computer in email addresses.