There is a refrigeration device like this, with an outer unglazed earthenware (terracotta) pot, and inner pot (which can be glazed, or vitrified pottery, or even some other material, but unglazed earthenware is usual), and a porous material (usually sand) between them. However, this is a modern device, and only just clears the 20-year rule - it was developed in Nigeria in the 1990s, by Mohammed Bah Abba, a teacher from a family of pot-makers.

His invention was one of the winners of the Time Magazine "Best Inventions of 2001". For more about this award and Mohammed Bah Abba and his invention, see:

• http://content.time.com/time/specials/packages/article/0,28804,1936165_1936254_1936632,00.html

• https://www.rolex.org/rolex-awards/applied-technology/mohammed-bah-abba

In English, it's usually called a "pot-in-pot refrigerator", and sometimes a "desert refrigerator". In Arabic, it's called a "zeer" (زير‎).

"Zeer" applies much more broadly than just to the pot-in-pot version; this name is used for a wide variety of clay pot coolers, which have been in use for a long time. Earthenware/terracotta pots have been around for a very long time, but the usual method of use is simply to put the jar in a shaded but windy place. If the pot contains water, the water soaks through and evaporates from the outside. If the pot contains something else, water can be poured or wiped on the outside for cooling. These types of jars used for cooling are called by various local names (e.g., "bojito" in Spain, "matka" in India), and work quite well in hot and dry weather.

There is (supposedly - I can't find the actual painting) Egyptian evidence of deliberate cooling from about 2500BC - slaves fanning jars. The usual assumption is that the jars contain water, and are being used to cool the room.

However, all of these pre-modern examples are just single pots, not the modern pot-in-pot version.