When our daughter was about one or two years old, she said WEE WEE because she couldn’t say Gary. That was the best she could do. So when I hear WEE WEE I think of toddlers NOT US PRESIDENTS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I still think it's from the Joker's drug dealing years. The term wee wee'd was in common use for stoners in the 70s and 80s. Where did he get the money, having never even had a real job as significant as running a lemonade stand.
I think of puppy raising.