The Dog, as created, had a rigid tail. After centuries of a cheerless existence, unappreciated by Man who made him work for his living, he implored the Creator to endow him with a wag. This being done, he was able to dissemble his resentment with a sign of affection, and the earth was his and the fullness thereof.
Observing this, the Politician (an animal created later) petitioned that a wag might be given to him too. As he was incaudate (tailless), it was conferred upon his chin, which he now wags with great profit and gratification — except when he is at his meals.