Douglas Harper's Etymology Dictionary
also garde-robe, "wardrobe," early 14c., from Old French garderobe "wardrobe; alcove; dressing-room" (Old North French warderobe; see wardrobe).
Wiktionary
n. 1 (context historical English) A store room or wardrobe. 2 (context historical English) A lavatory, especially in a castle and built into the outer wall, with vent directly over the moat or midden.
Wikipedia
Garderobe is a historic term for a room in a medieval castle. The Oxford English Dictionary gives as its first meaning a store-room for valuables, but also acknowledges "by extension, a private room, a bed-chamber; also a privy". Its most common use now is as a term for a castle toilet.
Usage examples of "garderobe".
Silvan lock him in the garderobe so she might shout at him through the door.
Trapping the laird of the castle in his own garderobe appealed to her sense of humor.
We entered the frigid drum tower, passed the well and the garderobe, then moved into the silent hall by the dining room and kitchen.
Could someone have been coming up a garderobe and through the window into the kitchen?
In this way, a garderobe could open a way into the castle, a way unprotected by security.
Down the hall, into the well tower, past the well and garderobe, into the spacious living room.
I unbolted the seat to the garderobe, yanked it up, and scrambled up on the ledge.
Sukie, who had been oblivious to his hidden life, the truth: that Andy Balachek had climbed through the west-side garderobe into the study.
The seductive vixen cleared the archway and disappeared toward the garderobe on the left.
The man had consumed such quantities that any other man would have sought the garderobe long before now.
If there was a garderobe, why on earth had Eirren told her to use the chamber pot?
Just say that you must go to the garderobe or some such thing, and that you hate to leave your king alone.
Adam the next morning coming from the garderobe, where he had been hurling the contents of his stomach for the past hour.
He could not go to the garderobe without stepping on one or the other of them.
As the door was flung wide she stepped out of the garderobe, hastily smoothing down her skirts.