In the 20s, the builders, when they were doing brick laying, they didn't have places to poop so it became
popular to just poop in somebody else's
bricks because you wouldn't want to poop on your own
bricks because you would have to put those bricks up.
It is used modernly as a term of warning.
Person A: I don't have anywhere else to throw this
trash so I'll just drop in on the floor of your
car.
Person B: Don't shit on my bricks,
mate. Shit on your own.