An Etymological Dictionary of Astronomy and Astrophysics

1. Any of numerous small Old World rodents of the family Muridae, especially of the genus Mus, introduced widely in other parts of the world.
   

2. Computers: A palm-sized, button-operated pointing device that can be used to move, select, activate, and change items on a computer screen (Dictionary.com).

Etymology (EN): M.E. mous (plural mis), from O.E. mus “small rodent;” cf. O.N., O.Fr., M.Du., Dan., Sw. mus, Du. muis, Ger. Maus, Pers. muš, as below.

Etymology (PE): Muš “mouse,” dialectal Lori, Laki miš; Mid.Pers. mušk; cf. Skt. muš-, muš-; Gk. mys; L. mus; O.E. mys; Ger. Maus.