Rear Admiral "Amazing" Grace Brewster Murray Hopper - While she was working on a Mark II Computer at Harvard University in 1947, her associates discovered a moth that was stuck in a relay; the moth impeded the operation of the relay.
While neither Hopper nor her crew mentioned the phrase "debugging" in their logs, the case was held as an instance of literal "debugging" - paving the way for the current definition of that term in development and engineering, and unofficially making her the first person to "debug" a system.
The remains of the moth can be found in the group's log book at the Smithsonian Institution's National Museum of American History in Washington, D.C.
en.wikipedia.org/wiki/Grace_Hopper