An alcarraza is an earthenware container, traditionally made in Spain. The container is filled with a liquid, then hung in a drafty place in the shade. The liquid seeps through the earthenware slowly and is evaporated by the action of the draft, lowering the temperature of the container and keeping the rest of the liquid cool.
The word for this container comes from the Arabic word al-karaz, meaning a pitcher.
The Collaborative International Dictionary
Alcarraza \Al`car*ra"za\, n.; pl. Alcarrazas. [Sp., from Ar. al-kurr[=a]z earthen vessel.] A vessel of porous earthenware, used for cooling liquids by evaporation from the exterior surface. [1913 Webster] ||
n. a jug, pitcher, etc. made of porous earthenware