Do-dah
Substitution word for a person, place or thing whose actual name escapes you at the moment.
Sandra: "Hand me the do-dah."
Mike: "Do you mean the potato peeler?"
Mike: "Are we cooking dinner tonight?"
Sandra: "No, do-dah is."
Mike: "Do you mean the potato peeler?"
Mike: "Are we cooking dinner tonight?"
Sandra: "No, do-dah is."