From Paragon Wiki Archive
- Common abbreviation of "City of X". A shorthand way of referring to both City of Heroes and City of Villains at the same time.
- The "X" comes from algebra where letters (commonly X) replace unknown numbers. Prior to the general adoption of CoX, players often typed "CoH/V", short for "City of Heroes/Villains". You will also see "Co*", which uses the asterisk (*) as a wildcard to represent either letter.