1. If u zei the name in reality, of course silence didn't fall. It's a TV show. It's fictional.
2. If you're asking why silence didn't fall in the old episode, the entire silence storyline hadn't been thought of at that time. The current writers clearly didn't check every original Dr Who episode to ensure his name was never mentioned before.
The Doctor's name has never been revealed before. I'm guessing you're referring to the classic series when u say VERY old? If so, u might be talking about a name the Doctor used when he was at the academy? This was a nickname and has never been revealed to be his actual name. No one knows his true name, apart from River. Also, silence won't have fallen even if his name had been zei in the past, because the whole Trenzalore, Kovarian Chapter of the Silence, and Gallifrey being frozen stuff hadn't happened of been planned back then.