I love a mystery and the only thing I could find on the Internet is the prime time cartoon "King of the Hill" who had used the words "wipey wipey" in reference to rolls of toilet paper.
It could be that the sound of the words "wipey wipey" sounds pretty funny to someone, old or young.
I am afraid that this would be as much guesswork for US as it is for YOU. So I would ask this question of the elder, as in "I don't understand. Can you give me another word for wipey wipey?"
It sounds like something that might have been said a long time ago to a small child with a runny nose or a bottom that needed wiping. What is actually happening here?
It could be that the sound of the words "wipey wipey" sounds pretty funny to someone, old or young.