Elonka wrote:
] ] Moth found trapped between points at Relay # 70, Panel F,
] ] of the Mark II Aiken Relay Calculator while it was being
] ] tested at Harvard University, 9 September 1945. The
] ] operators affixed the moth to the computer log, with the
] ] entry: "First actual case of bug being found". They put
] ] out the word that they had "debugged" the machine, thus
] ] introducing the term "debugging a computer program".
]
] There's a pic on this page with the actual moth taped into the
] journal. Though I'm not convinced that this is where the term
] bug or debugging came from. It sounds like the term was
] already in use, and then when they found this moth, they taped
] it in as a joke since they'd actually "found" a bug. Still,
] it's a great story. :)

Here's some more info on the origins of the computer "bug":

"The term in fact originates not with computer pioneers, but with engineers of a much earlier generation. The first example cited in the Oxford English Dictionary is from the Pall Mall Gazette of 11 March 1889:

Mr. Edison, I was informed, had been up the two previous nights discovering 'a bug' in his phonograph - an expression for solving a difficulty, and implying that some imaginary insect has secreted itself inside and is causing all the trouble.
It seems clear from this that the original 'bug', though it was indeed an insect, was in fact imaginary."

source:
http://www.askoxford.com/asktheexperts/faq/aboutwordorigins/bugs