semisecrecy
hugger-mugger
closehandedness
darkness
hidness
semisecret
mum
semisecretly
hypersecrecy
under one's hat
secernent
secretly
in secret
on the QT
on the Q.T.
closehanded
down low
subterranean
backstage
cloakedly
underhand
clandescent
secretive
hush-hush
occulted
private
pent
under wraps
confidentiality
ultrasecret
secretively
furtive
closeness
under the table
secrecy
covert
sensitive
backroom
hideling
under the covers
confidence
in petto
on the down-low
on the hush
hypersecretory
dark
closemouthed
a man's home is his castle
underwrapped
purdah