informed
private
privy signet
WC
accessory
alive to
anonymous
appreciative of
apprised of
awake to
aware of
back-door
backhouse
backstairs
basement
bathroom
behind the curtain
behind the scenes
bog
buried
can
clandestine
closet
cognizant of
comfort station
concealed
conscious of
convenience
covert
crapper
earth closet
feline
furtive
head
hep to
hidden
hidlings
hole-and-corner
hugger-mugger
in the know
in the secret
incognito
informed of
inmost
innermost
interior
intimate
inward
isolated
jakes
john
privier
priviest
outbuilding
ducal
latrine
mental-health
vocational
water-filled
divvy
kivi