Etiquette is also your default mode for social interactions, you know, when you are not trying to Con, or fast talk someone.... just fitting in, having a drink and shooting the shit...
It's the skill the allows you to go into the rough clubs or the fancy restaurants without making an ass of yourself, or getting shot. And it covers a lot more then just the words that come out of your character's mouth, but also his knowledge of acceptable wear, manners, slang, body language, social customs and norms.
For example a good roll on an Etiquette test for a socialite dinner party would tell you that you need to have a high standard of dress, not to swear like a sailor; and that farting and then sticking your finger in your ass to 'dirty sanchez' the girl next to you is not acceptable.