Proper nouns are names of specific people, places, or things. For example, "John", "London", and "Amazon" are all proper nouns.
"Mouth" is a common noun, referring to the general concept of a mouth.
If you're looking for a specific name for a mouth, you might be thinking of:
* A mouth of a river: This could be named based on the location (e.g., "The mouth of the Mississippi River") or have a specific name based on the location (e.g., "The Golden Gate")
* A mouth in a metaphor: If you're using a metaphor, you might give a mouth a name that represents its function or character (e.g., "The Mouth of Truth", "The Hungry Mouth of the Volcano").
Let me know if you have a specific context in mind, and I might be able to help you find the right word!