At 3:45 p.m., Grace Murray Hopper records 'the first computer bug' in the Harvard Mark II computer's log book. The problem was traced to a moth stuck between relay contacts in the computer, which Hopper duly taped into the Mark II's log book with the explanation: “First actual case of bug being found.” The bug was actually found by others but Hopper made the logbook entry.
I had always thought this is where the term "bug" came from, but the log says "First actual case of bug being found", which to me implies misperforming routines were called bugs prior to the "bug" being found.
This one incident has had so many variations and urban legend-ish twists.
This article itself even incorrectly lists the date as 1945 in one place, which is a common twist on the story, but incorrect.
(This computer didn't even come into existence until 1947, so the bug couldn't have been found in 1945).
For any know-it-alls who like to one-up people with the correct facts, here's the truth behind the story, best I can figure out:
This is indeed a real log entry book from September 9, 1947 (not 1945, as is sometimes reported)
Grace Hopper did not write the log entry book
Grace Hopper did not find the bug. She wasn't even there that day
Grace Hopper did make the story famous, though. Even though she wasn't personally involved, she found it funny, and liked to tell it, which is how she got associated with the story
This was not the first usage of the word "bug" (obviously, since "First actual case of bug being found" wouldn't have been funny). The earliest recorded usage of "bug" (in an engineering context) was Thomas Edison in 1878, but it surely predated him, as well. It was in common usage among engineers in the early 20th century
It was not the first usage of the word "debug", as is often attributed. We have a record of the word "debug" being used in 1945. (Maybe this is why some versions of the Mark II story are sometimes given as 1945). "Debugging" was used in the aviation industry before the software industry
The earliest recorded usage of the word "debug" in the context of software is 1952, but again, it probably predates its first record. Who knows if the word was already in use in 1947!