> Not really secret. A freemason friend of mine once explained to me that they're described as "a secret society" not because they try to hide their existence,

> Not really secret. A freemason friend of mine once explained to me that they're described as "a secret society" not because they try to hide their existence, but because they have secrets. i.e. shared secrets that they use as a means to authenticate to one another their membership and status. To me, this seems like an alternative and valid interpretation of the term to the one that you have inferred.