Bug
A bug is essentially the cause of a software glitch, such as an error or a problem that causes the software to crash or behave in an unexpected way. In some cases, a bug can also be a security vulnerability.
The term “bug” originated in 1947, at a time early computers were the size of rooms and made up of heavy mechanical and moving equipment. The first known incident of a bug found in a computer was when a moth disrupted the electronics of one of these room-sized computers.