The tiger-sheep approaches

As the Chinese year of the goat is approaching this four-characters idiom that begins with the character "yang" came to my mind:  

   You could ask what is the link between the year of the goat and the "sheep" of the idiom. The fact is, this is going to be the year of the "yang 羊", a character which has a wider meaning than simply "sheep" or "goat" in English or "pecora"/"capra" in Italian.

     In this idiom the word "yang" is in opposition with the word "hu" (tiger): The sheep/goat is here a symbol of weakness, while the tiger represents strength/power. 

This symbolical opposition derives from the other two characters, "zhi" (= nature, substance) and "pi" (= skin), used as opposites. This idioms, that literally translates as "character of a sheep - skin of a tiger", describes someone that appears something that he is not or that brags about some skill he has not: "impressive in appearance but lacking in substance".