Forgotten Nicknames

What happens to nick names when they stop being used?

When no one uses the special names to call someone with affection,

With extra love,

Using the special name only they are allowed to use,

Or moreover,

Only they know about it,

Because they kept it for you.

And it wouldn't make sense to anyone else,

Even if you explained the story behind it.

Where do the nick names go when they are not called anymore?

Do they miss being called too?

Because they sure are missed being heard.