"Eager beaver" is an English idiom used to describe someone who is overly enthusiastic and excited about doing something. A person described in this way often arrives early to begin their task or does more than he or she was expected to do. The meaning of the phrase "eager beaver" comes from the fact that beavers are especially industrious in the way that they build dams out of logs. This phrase first gained popularity in the United States during World War II, when commanding officers in the US Army used it to describe avid soldiers.
It is common for people who speak English to attempt to spice up their everyday speech with colloquial sayings and slang. Idioms, which are phrases that have gained a figurative meaning somewhat different from the literal meaning of the words they contain, also serve this purpose. The animal kingdom is a common source for idioms, since the behavior of animals is often colorful and unique. One of the most popular idioms referencing an animal is the phrase "eager beaver."
If a person is described in this manner, it means that he or she has great enthusiasm for the task at hand. For example, somewhat might say, "It was only her first day of work but she finished so much; she was a real eager beaver." Obviously, the literal meaning of the phrase is not in play in this example. The idiom simply provides a colorful way to describe the person in question.
In addition, this idiom can be used to indicate that a person is extremely anxious to get started on a project. This version of the phrase does not in any way indicate that the person will be skilled at the task. It simply means that the person wants to get going. As an example, consider the sentence, "You're here awfully early, so I guess you're an eager beaver." With this example, the early arrival of the person is an indicator of eagerness.
Beavers are known as extremely industrious animals because of the way that they bite through trees to get logs for their intricate dams. Comparing a person to one of these animals means that he or she must be especially impressive in his work ethic. The origin of the idiomatic expression "eager beaver" dates back to America in World War II, when soldiers anxious to impress their superiors were labeled in this manner.