pretty penny

English Idioms

A little birdie told me.
This means that someone told me something but I do not want to reveal who told me.
For example:
Joan: "I heard you are pregnant!"
Kate: "Who told you?"
Joan: "A little birdie told me."

Cross my heart and hope to die.
This is an expression used to say "I promise".
For example:
"I will pay you back all the money. I cross my heart and hope to die!"

Pretty Penny
This is used to say that something is very expensive.
For example:
"That car looks really expensive! I bet it cost you a pretty penny!"