Origin of the phrase “the shit has hit the fan”

I am not sure what the puzzle is.
I have no idea who coined it, but I would think that it’s meaning was sufficiently clear. Throwing something soft, easily frangible, and sticky into a rapidly spinning object is going to cause the thrown substance to be splattered out in all directions. Since it is sticky, it will cling to anything it touches, making cleanup a real problem. Given that it is inherently repellent, it is going to be even more abhorent that it is splattered across the floor, walls, ceiling, furniture, and any person or animal unfortunate enough to be in the way.

And, as long as the fan continues to spin, it is going to continue to make more of a mess, since some of it will continue sticking to the fan blades for quite a while.

Neither the Word Maven nor the Word Detective happens to address it, yet.