On: At

[panarky]

Same origin as the Spanish and Portuguese arroba[1], the Arabic ar-rubʿ (الربع). It's a unit of weight[2], "the fourth part (of a quintal), the term defined the load that a donkey or mule could carry."

[1] http://en.wikipedia.org/wiki/At_sign#Names_in_other_language...

[2] http://en.wikipedia.org/wiki/Arroba