Deesis (de’-e-sis): An adjuration (solemn oath) or calling to witness; or, the vehement expression of desire put in terms of “for someone’s sake” or “for God’s sake.”
Bozo: I swear on my mother’s grave that I would never cheat on you baby. You mean the world to me. For God’s sake, you’ve got to believe me.
Other: Your mother’s in the next room watching Jeopardy on TV. She’s alive. How can you swear on her grave?
Bozo: Oh–hmm–I should’ve said her burial plot.
Other: Where’s her burial plot?
Bozo: Well, I actually haven’t bought it yet. Here’s the brochure. I could swear on the brochure. Is that good enough for you baby?
Other: No, and who is that woman sitting next your mother on the couch?
Bozo: Um well, she’d an old friend. She stopped by to use the bathroom and decided to stay and watch TV with my mother. Don’t worry, there’s nothing between us–except you and my mother–ha ha ha.
Other: Have a good life Bozo. Good bye.
Definition courtesy of “Silva Rhetoricae” (rhetoric.byu.edu)