bug

Bug is an old English word of uncertain origin, possibly from Middle Welsh bwg (ghost, hobgoblin) or from a Germanic root meaning something that frightens. By the 16th century 'bug' meant a goblin or frightening creature; bugbear combined it with bear for an imaginary terror. By the 17th century the word had transferred to insects, particularly the bed bug — a household pest that genuinely inspired dread.

Thomas Edison used 'bug' in an 1878 letter to Theodore Puskas to describe flaws and difficulties in his inventions: '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 [bugs] as such little faults and difficulties are called, show themselves.' Edison's mechanical bugs preceded computing by seven decades.

Grace Hopper's team found the actual moth on September 9, 1947. Technician Bill Burke extracted a moth from Relay 70 of the Mark II at Harvard's Cruft Hall. The moth was taped into the logbook with the notation: 'First actual case of bug being found.' Hopper did not coin 'bug' — she recorded it. The word was already in engineering use; the moth made it literal.

Software bugs now cost the global economy an estimated $1.7 trillion annually. The 2003 NASA Mars Climate Orbiter was lost because one team used metric units and another used imperial — a bug in the most literal sense: a small, overlooked fault that cascades into catastrophe. Every programmer is paid, in part, to find the goblin in the relay.