Privy

Of or pertaining to some person exclusively; assigned to private uses; not public; private; as, the privy purse.

Secret; clandestine.

Appropriated to retirement; private; not open to the public.

Admitted to knowledge of a secret transaction; secretly cognizant; privately knowing.

A partaker; a person having an interest in any action or thing; one who has an interest in an estate created by another; a person having an interest derived from a contract or conveyance to which he is not himself a party. The term, in its proper sense, is distinguished from party.

A necessary house or place; a backhouse.

a small outbuilding with a bench having holes through which a user can defecate

a room or building equipped with one or more toilets

(followed by ‘to’) informed about something secret or not generally known; "privy to the details of the conspiracy"