What is the significance of the idea of a name? Of having multiple names? Of having a secret name known only to one’s self?

The name:

First of all, there's the name that the family use daily,
Such as Peter, Augustus, Alonzo or James,
Such as Victor or Jonathan, George or Bill Bailey—
All of them sensible everyday names.

Secret Names:

And that is the name that you never will guess;
The name that no human research can discover—
But THE CAT HIMSELF KNOWS, and will never confess.