The @ Symbol Started as a Medieval Unit of Weight

Every time you type an email address, you're using a symbol with a secret past. Long before the @ became the digital glue holding our online identities together, it was a merchant's shorthand for measuring everything from wine to wheat.

The @ symbol represents the arroba, a medieval unit of measurement used throughout Europe, particularly in Spain and Portugal. The word comes from the Arabic ar-rubʿ (الربع), meaning "quarter"—specifically, the fourth part of a quintal, which was roughly the amount a donkey could carry.

A Symbol of Commerce

In 15th-century Spain, clerks and merchants began using @ as shorthand in their accounting ledgers. It saved time and ink, two precious commodities when you're recording transactions by candlelight. The arroba measured 25 pounds (11.5 kg) in most Spanish regions including Castile, Aragon, and Catalonia, though Portugal used a slightly heavier version at 32 pounds.

But weight wasn't the only thing arroba measured. The symbol also denoted volume—specifically, the capacity of an amphora, those iconic clay jars the Greeks and Romans used for storing wine, olive oil, and grain. When Florentine merchant Francesco Lapi wrote a letter on May 4, 1536, he used @ to indicate an amphora of wine, roughly equivalent to 1/13th of a barrel or about 7 gallons.

From Ledgers to Keyboards

The @ might have faded into obscurity along with other obsolete measurements, but it got a second life thanks to the typewriter. When Christopher Latham Sholes designed the first practical typewriter in 1868, he included @ on the keyboard because it was still commonly used in commerce—particularly for indicating prices like "10 apples @ 5 cents each."

Then in 1971, computer programmer Ray Tomlinson needed a way to separate usernames from computer addresses in the first email system. He chose @ because it wasn't used in people's names and clearly meant "at" this location. In one keystroke, a medieval merchant's abbreviation became the most-typed symbol of the digital age.

Today, different languages have wildly creative names for @. In Swedish it's snabel-a ("elephant's trunk A"), in Greek it's papaki ("little duck"), and in Czech it's zavinac ("rolled-up fish"). But in Spanish and Portuguese, it's still called arroba—a 600-year-old word that refuses to retire.

The Oldest @ in the World

Want to see ancient @ symbols in action? The earliest known example appears in a 1345 Bulgarian translation of a Greek chronicle, where it represented "amen." But the oldest commercial use is Francesco Lapi's 1536 letter, now preserved for anyone curious about the paper trail that led to your inbox.

So the next time you send an email, remember: you're not just typing a symbol. You're using a piece of medieval accounting that outlasted empires, survived technological revolutions, and somehow became more relevant in the 21st century than it ever was in the 15th.