wild horses couldn't drag (something) from (one)
No amount of force, pressure, or enticement will make or convince one to divulge certain information. You can trust me with your secret—wild horses couldn't drag it from me! They thought they'd be able to make the financial advisor give up the passwords to his account, but it turned out wild horses couldn't drag the information from him.
wild horses
If you say that wild horses would not make you do something, you mean that nothing would make you do it. Wild horses wouldn't drag this secret out of me. Wild horses wouldn't make Nicola sell the house.