It isn’t just those, but horses and bulls have the biggest poops most people will ever see. So using them as reference for giant piles of unpleasant things makes sense.

Now, batshit? For one, have you ever been near where bats stay? The smell is so fucking intense.

But, bats are also known to flit around in a way that’s erratic when you rarely see their entire flight path. So they have a reputation for being less predictable, or a little crazy. At least that’s my understanding of how bats got referenced for someone being easily distracted, weird, or crazy. You know, “that old lady is a little batty, so don’t be surprised if she forgets to pay you”, or “that dude has bats in his belfry”.

How that got linked too batshit, I’m not certain. Back when I looked it up, the sources we have now didn’t exist., which ima go look the etymology of it up and see if there’s something newer to me. If there is, I’ll come back.