A computer meant to stay in one place, and the surface its interface imitates. Named for the furniture it replaced.
English compound of desk (Medieval Latin desca, from Latin discus, a disc, platter) + top (Old English topp, summit); a computer meant to stay on that surface, and the interface built to imitate the furniture it replaced.
Its own name is a small joke on furniture: a desktop is the screen standing in for the wooden surface a desk once was, borrowed word and all. What moved across into the screen was the metaphor, not the disc the deeper root once meant.