The ubiquitous, iconic “at” symbol’s roots are late medieval. Scribes perhaps added a swash to the d in the Latin ad (to or at). It was included on typewriters as early as 1885, but there was no place for @ in traditional typesetting, and there was no nook for the character in the California Job Case.
“@” has long been associated with retail sales and accountancy, but in 1971, Ray Tomlinson (23 April, 1941–5 March, 2016) was working on a way to communicate over a new computer network—the predecessor of the modern-day Internet. “I looked at the keyboard, and I thought: What can I choose here that won’t be confused with a username?” The at sign was an easy choice; it wasn’t commonly used in computing, so there would be no confusion. “It’s the only preposition on the keyboard.”