The ubiquitous symbol of internet era communications, the @ sign used in email addresses, is actually a 500 year old invention of Italian merchants, a Rome academic has revealed.
Giorgio Stabile, a professor of the history of science at La Sapienza University, claims to have stumbled on the earliest known example of the symbol's use, as an indication of a measure of weight or volume.
He said the @ sign represented an amphora, a measure of capacity based on the terracotta jars used to transport grain and liquid in the ancient Mediterranean world.
The first known instance of its use, he said, occurred in a letter written by a Florentine merchant on May 4, 1536.
Sent from Seville to Rome by a trader called Francesco Lapi, the document describes the arrival in Spain of three ships bearing treasure from Latin America.
"There, an amphora of wine, which is one thirtieth of a barrel, is worth 70 or 80 ducats," Mr Lapi informs his correspondent, representing the amphora with the now familiar symbol of an "a" wrapped in its own tail.
The Spanish word for the @ sign, arroba , also indicates a weight or measure, which was equivalent, at the end of the 16th century, to 11.3kg (25 lb) or 22.7 litres (six gallons).
"Until now no one knew that the @ sign derived from this symbol, which was developed by Italian traders in a mercantile script they created between the middle ages and the renaissance," Prof Stabile said. "The loop around the 'a' is typical of that merchant script."
The professor unearthed the ancient symbol in the course of research for a visual history of the 20th century, to be published by the Treccani Encyclopedia.
He said the sign, known to modern Italian cybernauts as la chiocciola (the snail), had made its way along trade routes to northern Europe where it took on its contemporary accountancy meaning: "at the price of".
Having hopped on to English typewriter keyboards in the early 20th century, it was selected as a rarely used symbol to separate user names from domain addresses by the American internet engineer Ray Tomlinson.
Prof Stabile believes that Italian banks may possess even earlier documents bearing the symbol lying forgotten in their archives.
"The oldest example could be of great value. It could be used for publicity purposes and to enhance the prestige of the institution that owned it," he said.
Internet users of various tongues have adopted metaphors ranging from an elephant's trunk to a monkey's tail and even a cinnamon roll to describe the now ubiquitous squiggle.
The inventors of the "snail" would doubtless be proud to learn that they were the progenitors of such a successful sign, also known, somewhat unromantically in English, as "commercial at".
"No symbol is born of chance. This one has represented the entire history of navigation on the oceans and has now come to typify travel in cyberspace," Prof Stabile said.
"Venice is the maritime city that continued to use the amphora weight unit the longest, but Florence is the foremost city of banking. The race is on to see who has the oldest document."