One may think “bugs” is the term used by programmers and other software experts to describe software errors. However, the terms “software bug” and “computer bug” are also frequently used by both non-IT professionals and members of the general public.1 

Have you ever wondered why these errors in software are called “bugs”?

The Definition of the Word

“In IT, a bug refers to an error, fault, or flaw in any computer program or a hardware system. A bug produces unexpected results or causes a system to behave unexpectedly. In short, it is any behavior or result that a program or system gets but it was not designed to do.”2

How did the Term “Bug” Come to Refer to Software Errors?

You might have thought that the word “bug” was first used when Harvard faculty members working in the Computation Laboratory linked a Mark II computer error to a moth caught in a relay. This bug was painstakingly taken out and taped to the still-present logbook. Though this was the very first computer bug in the world that was recorded, the term “bug” has been around for a much longer time.

With the development of computers, the term “computer bug” has become common among IT professionals. The term “bug,” however, was first used to refer to a machine-related issue. Ada Lovelace first mentioned the concept of a technical malfunction in 1843 when she discussed potential issues with the program cards used in Charles Babbage’s analytical engine. According to her theory, the cards in the analytical engine may issue incorrect orders as a result of insufficient operational information. She never referred to it as a bug, but Thomas Edison did.3

The term was first used to refer to a flaw or malfunction in a machine by Thomas Edison; however, it was not “the” computer bug. In actuality, the term has been widely used in the phone industry for a long time. According to an urban legend, the term was created as a result of a telephone noise that resembled a cockroach.4 Well, that doesn’t seem entirely believable now, does it?

software error

How did the Term “Computer Bug” Come About?

Long before computers and software were even considered, the word “bug” was frequently used to refer to mistakes or flaws in mechanical systems. However, the actual justification for the term’s first use is vague, to say the least, though it may have originated in early English parlance.4 

Some people speculate that it might have come from the Middle English word “bugge,” which is the root of the words “bugbear” and “bugaboo.” In this sense, the word “bug” is related to words like “goblin” and “gremlin,” which are also frequently used to describe mysterious mechanical malfunctions. Gremlin was first used by RAF pilots during World War II.5 Its meaning is much more akin to the word “gremlin,” where engineers frequently began to suspect that nefarious spooks were to blame for issues with engineering prototypes.4

So, the word “bug” or “bogey” component can be traced back to the 15th century, when it meant “Hobgoblin,” “devil,” or “ghost.” It is still common to refer to issues with machinery as with Bugbear, which first appeared in the 16th century in East Anglia. The term “bugbear” apparently has absolutely nothing to do with insects; it refers to a malevolent spirit.4

Regardless of its origin, in the mid-1800s, it became a popular term for mechanical faults whose causes have not yet been found or isolated and corrected. The term “bug” became widely used in engineering jargon after this point. As we’ve seen, the term was widely used by engineers throughout the late 1800s, and it only seems to have become popular around the turn of the century.5 

Isn’t that cool? Since you now know all about the term “bugs,” why don’t you check out the most famous ones in history? To read more such intriguing articles, you can also visit BYJU’s FutureSchool Blog.


  1. Where does the term “computer bug” come from? (n.d.). Retrieved June 28, 2022, from 
  2. What is a Bug? – Definition from Techopedia. (n.d.). Retrieved June 28, 2022, from 
  3. What is the First Bug in the History of Computer Science? (n.d.). Retrieved June 28, 2022, from 
  4. Why do we call them “Bugs”? – Simple Talk. (n.d.). Retrieved June 28, 2022, from 
  5. The Origin of the Term “Computer Bug.” (n.d.). Retrieved June 28, 2022, from