What Is a “Computer Bug,” and Where Did the Term Come From? Benj Edwards You’ve probably heard it before: There’s a “bug” in the software, causing something to malfunction or misbehave. What exactly is a computer bug and where did the term come from? We’ll explain. A Bug Is an Unintentional Error in Computer Software A “computer bug” or “software bug” is a term for an unintentional programming mistake or defect in computer software or hardware. Bugs arise from human error in hardware designs or somewhere in the chain of software tools used to create computer applications, firmware, or operating systems.