Grace Hopper (1906-1991), involved with the Mark-I programming project, starts to develop a series of base codes representing often used bit sequences. To these base codes are given named labels. These labels or codes will be called pseudo code, opcode, or mnemocode. With this she brings programming to a higher level.
During the project she defines a "Bug". It was this little creature that got stuck in the engine and stopped it working correctly. This bug got his immortality with its death.
A bug is an error in a program that causes the program to malfunction.