A moth stuck in a relay gave computing the word 'bug'

In 1947, engineers working on Harvard's Mark II computer found it malfunctioning and traced the fault to a moth trapped in one of its relays. Grace Hopper's team taped the moth into the logbook with the note 'first actual case of bug being found', a page now preserved by the Smithsonian. The term 'bug' for a technical fault already existed, but this literal case cemented it in computing folklore.

— Wikipedia contributors, Grace Hopper — Harvard Mark II logbook, 1947