Meaning

noun a small room (or recess) or cabinet used for storage space

noun a toilet in Britain

noun a tall piece of furniture that provides storage space for clothes; has a door and rails or hooks for hanging clothes

originFrom Middle English closet, from Old French closet, from clos (“private space”) + -et (diminutive suffix), from Latin clausum. Equivalent to close + -et, but generally applied in French solely to small open-air enclosures.

Etymology from Wiktionary, CC BY-SA 3.0