Dabi zubaan se: with a pressed-down tongue. The Rekhta dictionary defines it as speaking in a low voice, in a muffled voice, timidly.
Munh pe aur, peeth peeche aur: one thing to the face, another behind the back. Rekhta glosses it as a friend outwardly and an enemy inwardly. Peeth peeche badshah ko bhi bura kehte hain: behind his back, people speak ill even of the emperor.
Bichauliya: the one in the middle. Rekhta gives mediator, arbitrator, go-between and middleman. Its Hindi entry adds the person who arranges a marriage or an engagement.