on the quiet
• without anyone knowing or noticing; secretly or unobtrusively.
• "the deal was done on the quiet six months ago"
Similar:
in secret,
secretly,
furtively,
stealthily,
sneakily,
slyly,
surreptitiously,
covertly,
clandestinely,
on the sly,
on the side,
behind someone's back,
under cover,
under the counter,
on the q.t.,
