arroba

at (the symbol @); arroba (a traditional unit of mass generally equivalent to about 11.5 kg)

“volcaba él solo una caldera de doce arrobas de plomo fundido” — He turned over a twelve-arroba cauldron of molten lead by himself

Inherited from Old Spanish arroua, from Arabic اَلرُّبْع (ar-rubʕ, “one-fourth”), in reference to its forming one fourth of a quintal.