bug (the first computer bug)
loreThe 1947 logbook entry in which a moth trapped in a Harvard Mark II relay was taped down beside the note "First actual case of bug being found."
It is real and it is delightful, but it is not the origin of the word: engineers, Edison among them, were calling defects "bugs" decades earlier. The 1947 moth is the first case of a literal bug causing a fault, and the logbook survives in the Smithsonian. Grace Hopper loved to tell the story, which is how the two ideas got fused in popular memory.
The moth taped into a Harvard logbook on 9 September 1947 is the most repeated origin story in computing, and the detail everyone misses is the wording. The annotation reads "first actual case of bug being found," and that word actual is doing all the work: the engineers were making a joke that only lands because the term already existed. Bug had meant a fault in machinery since the nineteenth century, and Edison used it in that sense decades before anyone built a relay computer.
The attribution has drifted too. Grace Hopper was on the Mark II team and made the story famous through years of lectures, which is why it carries her name, but the Smithsonian's own catalogue notes the logbook was probably not hers and the handwriting does not match. She popularized it rather than wrote it, a distinction she would likely have enjoyed.
The moth is still there, flattened under yellowed cellophane, at the National Museum of American History. The story survives because it is a perfect artefact: a literal insect inside a machine, at the exact moment the profession was inventing a vocabulary for failure. It just is not the etymology, and telling it accurately is more interesting than telling it neatly.
Disputed / commonly mistold A popular version of this story is inaccurate - see the note above.
Also known as: first bug, computer moth, debugging origin
Sources
- Smithsonian National Museum of American History, object record 'Log Book With Computer Bug' (ID 1994.0191.01, dated 1947): engineers on the Harvard Mark II "found a moth stuck in one of the components" and "taped the insect in their logbook and labeled it 'first actual case of bug being found'". The same record sets the moth in its longer context: "American engineers have been calling small flaws in machines 'bugs' for over a century. Thomas Edison talked about bugs in electrical circuits in the 1870s." It places Grace Hopper "among those working on the Mark II in 1947" and states that "This log book was probably not Hopper's"
- P. A. Kidwell, 'Stalking the elusive computer bug', IEEE Annals of the History of Computing, vol. 20, no. 4 (1998), pp. 5-9, DOI 10.1109/85.728224, one of the two references the museum gives for its own record
- Grace Murray Hopper, 'The First Bug', Annals of the History of Computing, vol. 3 no. 3 (1981), pp. 285-286, the museum's other reference and Hopper's own account. Named without a link: the pre-1987 Annals volumes are not indexed in Crossref and no DOI for it was found. The widely repeated day, 9 September, appears in neither the museum's record nor any document read here