The computer mouse is so named because of its resemblance to the rodent of the same name. The body of the device resembles the rounded body of the animal, with the cord resembling a mouse's long tail. The mouse was invented by Douglas Engelbart in 1964, and while a member of his team came up with the name, no one remembered exactly who first called the device a mouse.
Engelbart first envisioned the computer mouse in 1961 while considering the possibilities of the planimeter, an engineering tool used to measure distances. His original design used two wheels mounted at right angles to measure the X and Y axis separately. Unfortunately, this made it difficult to track diagonal movement, a problem that was corrected in 1972 when Engelbart's teammate Bill English developed the first ball mouse.
Originally, the mouse was part of a set of input devices. The team developed a device based on telegraph keys containing five buttons, arranged like the keys of a piano. When the user switched to using the mouse for graphical input, these keys could be used for additional functions. The additional device never took off outside the laboratory, and the mouse and keyboard became the standard computer input devices.