From Latin 'claustrum' (enclosed space), from 'claudere' (to close) — same root as 'close,' 'include,' and 'exclude.'
A covered walk in a convent, monastery, or church, typically with a wall on one side and a colonnade open to a quadrangle on the other; also, a place of religious seclusion.
From Old French cloistre, from Latin claustrum (an enclosed place, a lock, a bar, a barrier), from claudere (to close, to shut, to enclose), from PIE *kleh₂u- (hook, peg, nail — something used to fasten a door). The same root gives Latin clavis (key), English close, clause, closet, and exclude. A claustrum was both the physical enclosure — a locked place, a confined
The word 'cloister' is related to an astonishing number of common English words through Latin 'claudere' (to close). 'Close,' 'closet,' 'clause' (a closed section of a sentence), 'include' (to close in), 'exclude' (to close out), 'conclude' (to close completely), 'preclude' (to close beforehand), 'recluse' (one closed away), and 'claustrophobia' (fear of enclosed spaces) all descend from the same root. German 'Kloster' (monastery) comes from the same Latin 'claustrum,'