why do they call it ...mouse - attached to the computer ... the sister of keyboard?
why not cat or dog? or any other animal and why not a technical term?
Because it looks like a mouse and has a tail 🙂
I imagine if it was furry, had four legs as well as a tail, purred when happy and snarled when hungry, was recalcitrant and never liked your new partners, it'd be called a cat. Alas, it was not meant to be.