down low
hugger-mugger
darkness
closeness
closehandedness
hidness
cloakedly
confidentiality
mum
hiding
under one's hat
semisecret
hush-hush
on the Q.T.
secretly
on the QT
semisecrecy
in secret
secretively
clandescent
hiddenness
covertness
closehanded
semisecretly
private
backstage
secernent
behind the scenes
on the down-low
under the covers
secretive
hypersecrecy
underhand
pent
subterranean
secrecy
occulted
public domain
masked
furtive
ultrasecret
backroom
dark
purdah
a man's home is his castle
hole-and-corner
confidence
on the hush
latency
hypersecretory