On September 9, 1947 Rear Admiral Grace Murray Hopper, USNR, (1906-1992) who worked with computer pioneer Howard Aiken, found one of the first literal computer bugs: a moth from Relay #70, Panel F, of the Harvard University Mark II Aiken Relay Calculator (now in the Science Center).
The Oxford English Dictionary entry for "debug" quotes the term "debugging" used in reference to airplane engine testing in a 1945 article in the Journal of the Royal Aeronautical Society. An article in "Airforce" (June 1945 p. 50) also refers to debugging, this time of aircraft cameras. Hopperís bug was found on September 9, 1947. The term was not adopted by computer programmers until the early 1950s. The seminal article by Gill in 1951 is the earliest in-depth discussion of programming errors, but it does not use the term "bug" or "debugging". In the ACMís digital library, the term "debugging" is first used in three papers from 1952 ACM National Meetings. Two of the three use the term in quotation marks. By 1963 "debugging" was a common enough term to be mentioned in passing without explanation on page 1 of the CTSS manual.
Source: wikipedia.org | harvard.edu