changing room; dressing room; locker room
Typically refers to a room where people change clothes, often found in public baths, swimming pools, or sports facilities. May include lockers.
I took off my clothes in the changing room of the public bath.
Lockers are lined up in the pool's changing room.
Compound of 脱衣 (undressing) + 室 (room). The exact historical derivation is uncertain, but the word is transparently formed from these elements.