The first computer bug was an actual real-life moth found trapped in a computer relay in 1947.
Why it is true
Admiral Grace Hopper and her team found a moth trapped in a relay of the Harvard Mark II computer. They taped the moth into the logbook with the note First actual case of bug being found. Although the term bug was already used to describe defects, this event popularized the expression in computing.
Source: Smithsonian
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