When you go swimming in freezing cold water, and in return your balls head up north in order to stay warm and protect the family jewels. Sometimes they go so far up north they even seem to disappear for awhile, which cause a great deal of discomfort.
Bob "Hey john did you go swimming today"
John "Yeah but the water was so cold that I got a major case of Canadian Balls"
Bob "Dude that sucks balls"