§31

In §31 Wittgenstein provides some sort of an answer to the questions raised in §30.  To understand an explanation like 'this is the king' Wittgenstein suggests that you must have already mastered he relevant game. So presumably Wittgenstein, in §30, was suggesting that to be able to ask what something is called you must already have mastered the relevant language-game.

David Stern:  To sum up: ostensive explanation cannot be the foundation for learning a first language, because ostensive explanation presupposes a knowledge of how names work, and more generally, a grasp of their place in language, a grasp which will include familiarity with how they are used in a variety of cases. (Wittgenstein's Philosophical Investigations an introduction.)