Something a douschebag, weak ass man says to a woman when she is shining too bright, being too happy or otherwise making him feel like the lesser he really is.
Someone telling someone else to tone it down usually has nothing to do with race, it's because the other person is full of shit.
He/she didn't like being told that he/she was full of shit even if the person that said tone it down had a point, and the one they said to tone it down to had no point, but still looked for anything he/she could to be argumentative over just to be argumentative, a stop sign being red not being good enough of an answer not to get argumentative about it without good reason, for example.
James mom: (starts walking to James room)
James: oh crap (closes pornhub)
James: shit I need to clean this cum up fast and tone my pen down
James: (gets tissue and cleans cum)
James mom: (walks in)
James: Crap!.. Hi mom!
James mom: Hi James is that a boner?
James: (puts hands on crotch) Nope!
James mom: Ok just remember to do the dishes!
James: Phew!
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 baseballhit him in the nuts.
Man, I just watched the funniest nutshot video ever.