Merriam-Webster defines the word bug as “an unexpected defect, fault, flaw, or imperfection.” In 1946, the 1st ever case of a software bug was reported in an early electro-mechanical computer called the Mark II. An actual moth got trapped in the relay of the computer and caused it to malfunction. The moth was removed and taped into a log book and recorded as the 1st actual case of a “bug” being found! The log book (with attached moth) is on display at the Smithsonian National Museum of American History. Now, how’s that for error tracking!
This term bug however was coined earlier as records show that Thomas Edison used it in 1878:
“It has been just so in all of my inventions. The first step is an intuition, and comes with a burst, then difficulties arise—this thing gives out and [it is] then that ‘Bugs’ — as such little faults and difficulties are called—show themselves and months of intense watching, study and labor are requisite before commercial success or failure is certainly reached.”