ground-hog (n.)

also groundhog, "American marmot," 1784, from ground (n.) + hog (n.). Also known colloquially as a whistlepig, woodchuck, and compare aardvark. Ground Hog Day as a weather forecasting event is first recorded 1869, in an Ohio newspaper article that calls it "old tradition;" the custom though not the name, attested from 1850s.