In this article below in vanity fair they use the actual phrase " knows where the bodies are buried. " maybe wrong bodies in there eyes but ..
"That’s not to say that Flynn might not know where the bodies are buried, if there were bodies to be found"
https://www.vanityfair.com/news/2017/03/mike-flynn-immunity
Then in a different article by Just Security:
They talk about how odd it is that the Flynn deal was made PUBLIC ( Q drop Lawmakers make public ) And Flynn's Attorney made a few cryptic messages knowing what we are starting to know.
Although Flynn’s lawyer, Robert Kelner of Covington & Burling, refused to comment for the article, he tweeted out a statement teasing that “General Flynn certainly has a story tell, and he very much wants to tell it, should the circumstances permit.”………
"The fact that Flynn and his lawyer have made his offer publicly suggests that he has nothing good to give the prosecutors (either because he cannot incriminate others or is unwilling to do so). If he had something good, Flynn and his lawyer would approach the prosecutors quietly, go through the proffer process in confidence, and reach a deal. Why? Because prosecutors have an interest in keeping their investigation secret, and Flynn’s lawyer knows that. The last thing Flynn’s lawyer would do if he thought he had the goods would be to go public, because that would potentially compromise the criminal inquiry and would certainly irritate the prosecutors…"
https://www.justsecurity.org/39426/explainer-flynns-request-immunity/