Y2K is an acronym for "Year Two-Thousand." (K being short for Kilo, the Greek word for thousand.)
Y2K was a proposed computer-related catastrophe. Some suggested that computers would not correctly track the date changing from 1999 to 2000, but rather change from 1999 to 1900. It was argued this error would effect vital computer systems controlling such services as electrical power, water processing and food distribution.
Some people suggested Y2K would cause wide-scale social chaos, creating a media scare. However, as the new year rolled in, few if any Y2K related problems were reported. Much more significantly, many identical critical infrastructures, some "fixed", some not, could be compared for their performance - in absolutely NO case was there a fault in a "not fixed" infrastructure that did not also occur in one that was "fixed". Thus there was provably no impact from any of the fixes, except for a vast transfer of cash from those doing "Fixes" to those paying for them.
Cyber threat mythology became a major aspect of propaganda as of this turn of the so-called 21st century - the idea that computers had many hidden threats seemed to resonate with the public. Millenial vision also played a role - the idea being that somehow "control of information assets" would have unanticipated benefits for the public. The real benefit, as proven after 9/11, was that creditors could continue to track debtors through even the worst disaster and physical destruction of the offices of creditors.