To work hard and persistently, often to accomplish a goal; to work like a beaver, building or working industriously.
Present participle of beaver (verb), from the animal beaver known for its industrious dam-building. The verb developed metaphorically because beavers are famous for working tirelessly.
This word proves that animals shape our language in unexpected ways—because beavers are such famous workers, we turned their name into a verb meaning to work hard, and now a 'beaver' is slang for a hard worker even if people don't think about the actual animal anymore!
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