word-forming element, ultimately from cybernetics (q.v.). It enjoyed explosive use with the rise of the internet early 1990s. One researcher (Nagel) counted 104 words formed from it by 1994. Cyberpunk (by 1986) and cyberspace (1982) were among the earliest. The OED 2nd edition (1989) has only cybernetics and its related forms, and cybernation "theory, practice, or condition of control by machines" (1962). 

Cyber is such a perfect prefix. Because nobody has any idea what it means, it can be grafted onto any old word to make it seem new, cool -- and therefore strange, spooky. ["New York" magazine, Dec. 23, 1996]

As a stand-alone noun, cyber, it is attested by 1998 as short for cybersex (which is attested by 1995).