LastWriterStanding explained it during Beta. Jyan / Jyansei are made up words (that are supposed to sound asian), because they weren't allowed to use an actual Asian word for the PC. It's supposed to mean something like "Warrior / Martial Art Master". Actually, only NPCs who have some knowledge about martial arts are refering to you as "Jyan / Jyansei" so it's also a mean to get information about the NPCs (Civilian or Martial Arts Master).
And Cricket... They didn't want to use "Grasshopper" to avoid legal issues with a movie brand or something like that.