This is a picture of a British bird called the great-tit. For the more ridiculous among us I am bound to say that the only bad connotations associated with this bird is its liking for perforating the milk bottle top should it be left for long on your doorstep and stealing the cream from the top of the milk-the little bugger!

As for idioms. If you are a native born English user of English idioms, it's the meaning of the whole and not just one word. Very often, because there are so many of these expressions we don't bother to delve into how an expression means what it does mean, and we know it means. I tell my students to just accept an expression means what you are told it does mean and don't bog yourself down thus inhibiting your path to fluency by analysing how it means what it does. However, when you can speak the language well that is the time to start taking it to pieces if you so choose to do so. So, in other words don't tackle your learning 'arse about face.'