Also to be noted is that this is not exactly a pun by your definition. Because “fiesto” is not a word it cannot have different meanings or applications. In fact it has none at all. Second, though it does sound like to two true words, it is not a word itself so it cannot be different in meaning to them as it has no meaning at all. Finally, how do you have a play on words without using real words?

Perhaps then, you have come up with a new brand of literary humor. jonopun: the humorous creation of a non-word which is nearly alike in sound to one or more true words for the purpose of rhyming.