On 9 September 1947, engineers working on Harvard’s Mark II found a moth lodged in a relay.
They taped it into the logbook and wrote “First actual case of bug being found.”
The moth is real, but the popular origin story sadly is not.
Engineers already used “bug” for a technical fault.
Thomas Edison was using it in the 1870s.
The joke worked precisely because the word was familiar.
Grace Hopper was on the Mark II team but The Smithsonian notes that the logbook probably wasn’t hers.