The English language is full of animal idioms, such as the one below:
lead a dog's life - to work hard and yet be treated in an unkindly manner
ex. She is leading a dog's life ever since she married that awful man.
horse around - rough or noisy play
ex. Mrs. Hopkins told her children to stop horsing around so that they can start praying.
I have never seen a beaver in my entire life, so I'm not sure why it was chosen for this particular idiom. I have a hunch though that it's mainly because of the rhyme thing in the English language. :-)
eager beaver - a person who is always eager to work or do something extra
ex. She's a real asset to the company because of her eager beaver attitude.
The English language truly has a rich and sometimes hard to understand vocabulary and idioms, one of which is the idiom below:
dog-eat-dog - willingness to fight, get hurt and hurt others to get what one wants
ex. He raised his son to be strong and independent, knowing it's a dog-eat-dog world out there.
