The 'at' sign probably originated in the Middle Ages; either as an abbreviation of the Latin 'ad'(at,towards,by) or as a mercantile abbreviation for 'amphora'. The symbol has endured to this day in Spain, Portugal and France, as the unit of weight 'arroba', which is equal to about 15litres or 10kg. It also occurs in old German Legal texts, while in English-speaking countries it served as an assignment of price (5eggs @ 20cents).
From these distant beginnings, the symbol made its way onto typewriter keyboards, where it waited to be chosen by the author of the world's first e-mail when he was looking for an address component. In 1971, Ray Tomlin son needed a sing that could be found on all common keyboards but wasn't a letter of the alphabet. With the @ sign he managed to provide an unambiguous separator between the two parts of an e-mail address.
The @ sign around world
The @ sign is quite unusual in appearance-which has caused it to be given all sorts of imaginative names around the world.
Monkey's tail South Africa
Cat's tail Finland
Maggot, worm Hungary
Snail Italy, France, Isrel, Korea,UkrainEsperanto
Cinnamon twirl Sweden
Ear muff Iceland
Pig's tail Denmark