Definition
Used to emphasize that what one has just said or promised is absolutely true and sincere.
"I didn't eat the cookies, cross my heart and hope to die," the child said, holding up his hands.
“I promise, I will never tell anyone your secret, cross my heart and hope to die,” she whispered.
“I swear I put the money in a safe place, cross my heart and hope to die!” he said, looking a bit nervous.