Closet

From the Oxford Dictionary:

NOUN

1. chiefly North American, A cupboard or wardrobe, especially one tall enough to walk into

2. used to reveal a state of secrecy.....

ADJECTIVE

secret; covert

VERB

shut (someone) away, especially in private conference or study

ORIGIN

late Middle English (denoting a private or small room): from Old French, diminutive of clos 'closed' (see close1).