Atari 5200
While it was being designed, the Atari 5200 called the "Atari Video System X - Advanced Video Computer System."  Atari protected the design with a codename, "Pam," after a female employee at Atari.  A rumor said that "Pam" or "PAM" actually stood for "Personal Arcade Machine."  This was because most games for the system were based on existing arcade games. Actual working Atari Video System X machines, whose hardware is 100% identical to the Atari 5200 do exist, but they are extremely rare.