I'm paraphrasing, but not by much:
Me: "Max come here for a second."
Maxman: "Okay, I'll be there in a chippy."
Me: "You mean jiffy."
Me: "The saying is, 'I'll be there in a jiffy.'"
Maxman: shrugs with the whatever look on his face - I know what this look means because I invented it. "Okay mom, I'll be there in a chippy."
Have been thinking about this and I can't think of any reason that jiffy makes more sense than chippy. Will refrain from correcting this in the future.