Why are they called "bugs" anyway? Here's a little history lesson paraphrased from a Michigan State University web site by Todd E. Van Hoosear:

Dr. Edward Tenner, "Why Things Bite Back: Technology and the Revenge of Unintended Consequences" (Random House, 1996) , a historian of science, quotes Thomas Edison using the term "bugs" as early as 1878, for flaws in a system. Tenner points out that the word was a common "shop" term even in Edison's time for such systems faults. The carryover to computers--systems all--is logical. Why "bug" was used for "fault" may be induced from the fact that the term appeared as early as the 14th cent. to mean "an object of dread" ("Concise Oxford Dictionary of English Etymology"), from the Welsh word "bwg" for "hobgoblin."

Grace Hopper, a Lieutenant in the US Navy during World War II, and assigned to the Bureau of Ordnance, was instrumental in popularizing the term after discovering the cause of a computer malfunction. According to the Naval Historical Center, "a moth was found trapped between points at Relay # 70, Panel F, of the Mark II Aiken Relay Calculator while it was being tested at Harvard University, on 9 September 1945. The moth was affixed to the computer log, with the entry: 'First actual case of bug being found'." The story of the moth has since become a legend in computer circles. Grace Hopper eventually retired from the Navy with the rank of Rear Admiral in 1985.