No, we’re not referring to the noun version of this word, which means a toilet (heard mainly in the UK). We’re talking something a little more surreptitious here. Privy is an adjective meaning secret or private, most especially, admitted as one disclosing in something slightly cloak-and-dagger.
Example: Todd arrived early to the weekly project meeting, only to hear the supervising contractor and his bookkeeper discussing cheating his client. Now that he was privy to their illegal behavior, he had to decide how to secure proof.