The word cloister means closed and was originally used for the part of a monastery which was closed to public access. When its main feature became a grass square surrounded by an arcade, people began to use 'cloister' to refer to the enclosing element: the arcade.
Cloisters are the most significant legacy of the ancient world's peristyle gardens. They can be wonderful spaces:
It cannot be beyond the wit of the modern world to find a new use for such a brilliant garden type.
Islamic courtyards, as found in mosques and madrassahs, are related to cloister gardens. And they demonstrate how the building type is just as well suited to a hot southern climate as a cold northern climate.
Christian cloister (above) and Islamic courtyard (below)