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The First Computer Bug Was Seventy Years Late

The word bug was seventy years old before the moth. The moth was also not a bug.

An illustration of a green moth with its wings spread, beside a shield bug drawn in black outline, both seen from above on a pale grey background.
A moth and a shield bug. Illustration: Binary & Thread.

In 1947, a moth got stuck in the Mark II computer at Harvard University. Engineers taped the insect into their logbook and wrote "first actual case of bug being found." The logbook sits in the Smithsonian National Museum of American History in Washington. You have probably seen the photo. Everyone tells it the same way. The moth gave computing the word bug. It is a clean story.

A page of graph paper from the Mark II logbook, filled with handwritten times and notes. Halfway down, a small brown moth is held flat under a strip of yellowed tape, with the handwritten line "First actual case of bug being found." beneath it.
The Mark II logbook page, with the moth taped in above the line "First actual case of bug being found." US Navy photograph NH 96566-KN, courtesy of the Naval Surface Warfare Center, Dahlgren, 1988. Public domain, via Wikimedia Commons.

Except the word was already old. The Smithsonian's own description of the logbook says that American engineers had been calling small defects in machines "bugs" for over a century. Thomas Edison used the word for glitches in electrical circuits in an 1878 letter. That was sixty-nine years before the moth.

In 1889, a London newspaper called the Pall Mall Gazette described Edison staying up two nights to find a "bug" in his phonograph. The paper explained the phrase for its readers. An imaginary insect had secreted itself inside the machine and was causing all the trouble. A nineteenth-century newspaper was defining the word for a general audience.

By 1934, Webster's New International Dictionary gave "a defect in an apparatus or its operation" as the third definition of the noun bug. The word debug appeared in a 1945 issue of the Journal of the Royal Aeronautical Society. Two years before the moth, someone was already debugging.

So the logbook line is not an origin. It is a pun. Fred R. Shapiro, a linguist, traced the word's history. He reads "first actual case" as a note on novelty. The team already knew bug meant fault. They were flagging the surprise of a real insect in a machine full of figurative ones. That is the whole joke.

Grace Hopper, later a Navy rear admiral, was on the Mark II team in 1947. The Smithsonian says the logbook itself was "probably not Hopper's." She and the team helped popularise the terms computer bug and debug. The Computer History Museum credits her many public talks with making the incident famous. In 1981 she wrote an article called "The First Bug" in the Annals of the History of Computing.

The insect in the logbook is not, by taxonomy, a bug. A bug, to an entomologist, is a member of the insect order Hemiptera. Aphids. Cicadas. Bed bugs. The moth was a Lepidoptera, a scale-winged insect. The first actual case of bug being found was, by taxonomy, a false positive.

The logbook was transported to the Smithsonian from the US Navy's Naval Surface Warfare Center. It is not on display. It sits in a drawer. The catalog lists its materials as paper, cloth, and tape. The rest is ink and "biologicals." The moth is still in it.

The design from this story

We made a T-shirt with a low-poly bug on it: six legs, flat planes, and no moth anywhere.

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