throw away the key

An ellipsis of lock someone up and throw away the key.

throw away the key (third-person singular simple present throws away the key, present participle throwing away the key, simple past threw away the key, past participle thrown away the key)

1. To never release someone (e.g., from prison).
   • 1995 November 19, “Senators Pete Domenici and John Breaux Discuss the Shutdown of the Federal Government”, in CBS Face Nation:

     Let's get these men together in a room and I would suggest feed them bread and water and throw away the key until they come together