Why would Ned change the child’s name when it was just given to him by his dying mother? Her naming was obviously influenced by Robert’s vengeance against the Targs, so she would name him something inconspicuous. She knows she is dying, and she knows that Ned is the only person who can protect her child, so she gives…

I’ve read speculation that Jon’s given name is Jaehaeryrs, based Lyanna seeming to speak a thread syllable name to Ned and the Targaryen tradition of baby names. The history of the name would also suit him: http://awoiaf.westeros.org/index.php/Jaeh…