A mouse was a manual input device on computers of the 20th and 21st centuries. The device was known as a mouse because a cord, which connected the device to the computer, resembled the tail of a mouse. A person provided input to a computer via the mouse by rolling the mouse on a flat surface and clicking buttons.
Montgomery Scott mistook the device for an audio-input device when he traveled back in time to 1986, speaking into it when attempts to talk directly to the computer were unsuccessful. (Star Trek IV: The Voyage Home)