Probably has something to do with hernias. Someone didnt understand it so they went around and exaggerated about them and it went from there.
You’re right. It is possible to get a hernia from lifting heavy. I would say it is rare but then I would also have to acknowledge the guy in my gym who just had one weeks ago. Since I see him often, I would relate that to HOW he trained (excessively…while going to school…while working 2 jobs…after breaking up with his girlfriend…and taking all of this out on the weight room for 2+ hours) along with the fact that he was more than likely prone to it since birth and not simply because he was lifting heavy weight.
A hernia into the scrotum through the inguinal canal could occur in some people. However, worrying about things like this when they have never happened to you would be a little like worrying about getting hit by falling meteorites while walking to the car. If you quit because of the possibility, you won’t get anywhere.