(Sektion 42: Philosophische Untersuchungen von Ludwig Wittgenstein).
Leading up the famous 43rd aphorism, Wittgenstein discusses the possibility of novelty in the builder language (see Philosophische Untersuchungen 2), which Augustine's copy theory of meaning is a complete description of. Wittgenstein asks if perhaps the language might be complex enough to allow the introduction of new words into it? That is, can there be a word in a language that does not refer to anything? A asks B for a tool that does not exist: A calls out "X". According to a copy theory of meaning, this word would have no meaning, because there is nothing to which it refers, it is referenceless, or meaningless. Wittgenstein is here drawing our attention to the richness of human language in describing a context for such novelty in language--perhaps, he suggests, it is a kind of joke.
42. But does some name that has never been used for a tool have a meaning in that language-game?--Let us assume that "X" is such a sign, and A gave this sign to B--now, such signs can also have a place in the language-game, and further B might answer them with a shake of the head. (One can think of this as a kind of joke between them.)