A Real Moth Found in Harvard's Mark II Computer

Around 1947, operators traced an error in Harvard's Mark II computer to a real moth trapped in a relay. After finding the problem, the operators taped the insect into the logbook with the note: 'First actual case of bug being found.' This unusual incident documented a physical creature disrupting an early computing system.

It is surprising to discover that this famous event did not actually create the word bug. While many people assume computer operators invented the expression during this discovery, the term was already established engineering jargon by the 1870s. The note in the logbook was an intentional joke, celebrating a literal insect causing trouble instead of the figurative bugs engineers had discussed for decades.

For an ordinary reader, this means that finding a real moth in Harvard's Mark II computer was a humorous coincidence rather than the birth of a technical phrase. The operators were simply making light of an existing term that had described technical errors long before that 1947 discovery.