means a small rodent with a pointed snout, rounded ears, and a long thin tail; also the hand-held device that moves a pointer across a computer screen.

from From Old English mūs, a word that has barely changed in thousands of years — it traces straight back to Proto-Indo-European *mūs, the same ancient root that gave Latin mus, Greek mŷs, and Sanskrit mūṣ. The computer sense is a modern joke: the first models, built in the 1960s, were small lumps trailing a wire-thin cord, and someone thought they looked like a mouse with a tail.