A codename is a secret or alternative name used to refer to something or someone, especially in order to keep their identity or purpose hidden. Full definition
He mentions, «The project codename for Pokémon Switch is hidden somewhere in my timeline.» (gamingintel.com)
First revealed all the way back in March 2014 under codename of Project Morpheus, the final version of the kit was unveiled a year later and the name PlayStation VR was given to it at the 2015 Tokyo Game Show (TGS). (vrfocus.com)
It was first introduced as codenamed Project Spartan on January 21st, 2015. (thewindowsclub.com)