My friend told me kiwis (the fruit) were also called monkey balls. Bear in mind I was probanly 10 at the time and very naive even by 10 year old standards. I thought he meant like because they were hairy and monkeys were hairy. He very well could of, but he was a lot less naive than me and i think he knew what he was doing.
One day i had a kiwi at school and my teacher said something about it. Naturally i wanted to show off my knowledge and told her they were called monkeyballs. She gave me an odd look and kind of moved the topic on. I didn't know why she gave me the look. Didn't realise the potential of that comment till much later in life.