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mountain beaver

noun
  1. a small, burrowing rodent, Aplodontia rufa, of the Pacific coastal region of North America, considered the most primitive living rodent.
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Origin of mountain beaver

An Americanism dating back to 1880–85
Also called sewellel.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018