You might choose to use a word for "dog" as "woof woof" because it sounds like a dog but you can't use a word for "country" that sounds like a country.

你可以用“汪汪”这个词来表示“狗”，因为它听起来像只狗，但你却无法使用一个听起来像国家的词，来表示“国家”。