Why are errors called “bugs”?

When a programmer says there is a “bug” in the code, few people realize that it wasn’t always a metaphor, but a reality. In 1947, Grace Hopper was working on one of the first computers (Mark II). 

Suddenly, the machine stopped working. When technicians opened it, they found an actual moth stuck between the relay contacts, where it had burned and broken the circuit. Grace pulled it out, taped it into her logbook, and wrote: “First actual case of bug being found.” Since then, every technical error has been called a bug.