Term derived from Johann Gauss who was a mathematician who studied and worked with electro-magnetic fields. Degauss is a method of erasing magnetic media by passing magnetic media through a magnet field more powerful than the media itself to rearrange the magnetic particles.
Degaussing was first used by the British Royal Navy in the 2nd World War. An electro-magnetic cable was inserted on the inside and around each warship as a safeguard against magnetic mines. Each time a ship came into harbor it was degaussed using this cable. An electrical current was passed through the cable neutralizing the magnetic field causing the magnetic to detach.
When degaussing a monitor the degauss demagnetizes the CRT, fixing possible color impurities. After either the degauss button is pressed or the monitor is manually degaussed the degaussing circuit will be activated and then deactivated after a few seconds. Older monitors that didn't include this feature had to be degaussed using a handheld monitor degauss.