let something slip
give the game away
slip
let slip
out with it
secret of Polichinelle
tip one's hand
skeleton in the closet
skeleton in the cupboard
something nasty in the woodshed
resecrete
on the hush
keep a lid on
off-the-record
out
mis-
stitch-up
disembosom
let the cat out of the bag
make known
roll
spill the beans
secretively
covert
yield up
exposure
secretly
on the down-low
misrelease
mitch
under the covers
divulgence
closehanded
divulgement
underhanded
secret
under the rose
semisecretive
divulgation
furtive
underplot
babble
latently
subdititious
anecdote
keep from
fredaine
accidently
shoot off at the mouth
secretable