BogoMIPS. What does it mean?

Considering Linux OS, we can see a text “BogoMIPS”. It also displays a number. What does it mean?

BogoMips is an unscientific measurement of CPU speed made by the Linux Kernel when it boots to calibrate an internal busy-loop. The value can be used to verify whether the processor being used is in proper range of similiar processors.

BogoMips is Linus’s own invention. His kernel version 0.99.11 needed a timing loop (the time is too short and/or needs to be too exact for a non-busy-loop method of waiting), which must be calibrated to the processor speed of machine. Hence the kernel measures at boot time how fast a certain kind of busy loop runs on a computer. This is unscientific method of measurement of MIPS so is called Bogus (fake).