What is the origin of the idiom "busy as a beaver" and when to use it?

The phrase "busy as a beaver" is believed to have originated in the 18th century, and it is a reference to the industrious and hardworking nature of beavers, which are known for their ability to build dams and lodges. It is used to describe someone who is very busy and active, working hard to complete tasks and achieve goals. It is often used to convey a sense of admiration or respect for someone's work ethic.