The at sign, , is an accounting and invoice abbreviation meaning "at a rate of" (e.g. 7 widgets @ £2 per widget = £14), now seen more widely in email addresses and social media platform handles. It is normally read aloud as "at" and is also commonly called the at symbol, commercial at, or address sign.
The absence of a single English word for the symbol has prompted some writers to use the French arobase or Spanish and Portuguese arroba, or to coin new words such as ampersat and asperand, or the (visual) onomatopoeia strudel, but none of these have achieved wide use.
Although not included on the keyboard of the earliest commercially successful typewriters, it was on at least one 1889 model and the very successful Underwood models from the "Underwood No. 5" in 1900 onward. It started to be used in email addresses in the 1970s, and is now routinely included on most types of computer keyboards.
The earliest yet discovered symbol in this shape is found in a Bulgarian translation of a Greek chronicle written by Constantinos Manasses in 1345. Held today in the Vatican Apostolic Library, it features the @ symbol in place of the capital letter alpha "Α" as an initial in the word Amen; however, the reason behind it being used in this context is still unknown. The evolution of the symbol as used today is not recorded.
It has long been used in Catalan, Spanish and Portuguese as an abbreviation of arroba, a unit of weight equivalent to 25 pounds, and derived from the Arabic expression of "the quarter" (الربع pronounced ar-rubʿ). A symbol resembling an @ is found in the Spanish "Taula de Ariza", a registry to denote a wheat shipment from Castile to Aragon, in 1448. An Italian academic, Giorgio Stabile, claims to have traced the @ symbol to the 16th century, in a mercantile document sent by Florentine Francesco Lapi from Seville to Rome on May 4, 1536. The document is about commerce with Pizarro, in particular the price of an @ of wine in Peru. Currently, the word arroba means both the at-symbol and a unit of weight.