To re-arrange words like that is called to permute, the ancient Semitic people used it as a way to understand the universe, cosmology, divine and celestial beings and nature all around us.
It was a word joke - and you threw in a great straight line to set it up. A "truism" is a self-evident or all-too-obvious truth. Obviously secrets are best left unsaid because once said they are no longer secrets.
Yes and if a secret is known it wasn't a secret at all, at last ontologically speaking, so I guess there are no secrets in the universe, but a lot of people with missing information. (I think the cheese is making me light headed)