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