What is proper noun for bathroom?

There isn't a proper noun for "bathroom." Proper nouns are used for specific people, places, or things, like:

* People: John, Mary, Queen Elizabeth

* Places: London, Mount Everest, The Grand Canyon

* Things: The Mona Lisa, The Empire State Building,

Since "bathroom" is a common noun, it refers to any room used for bathing or toileting. It doesn't have a specific name like a person, place, or thing.

However, you could use a proper noun for a bathroom in certain contexts:

* If it has a specific name: "The Powder Room" or "The Guest Bathroom"

* If it is part of a larger entity: "The Royal Bathroom at Buckingham Palace"

Let me know if you have more questions!