hush your gums, made by MasTiemp01, means to shut your mouth basically. Therefore, if you for example, for an insult, someone might tell you that you don't deserve teeth so you should be able to speak, so hush your gums.
It is said of the situation where a person has the bad luck to make contact with his testicles against an undefined surface or object, intentioned or not.
Given the nature of the word, it is more appropriate to design cases where the interaction is made with a moving object, for example, a ball.
Although it is extremely painful for the victim, it tends to be considerably funny to people who witness it.
Today in the baseball game the pitcher took a nutshot; the baseball hit him in the nuts.
Man, I just watched the funniest nutshot video ever.