Stuff that we just don't usually talk about
Yes, there are several secrets I have promised not to pass on... If someone says, "don't tell this", I won't. They have trusted me to not pass on something very private. I would feel bad if I repeated the secret, I'd know in my hear that I had betrayed them, even if they never found out.
To Joy - no doubt you have been a good friend and confidant. I too have kept such secrets. A heavy promise at times, but I keep my promise none the less.