Phrases such as “batshit nuts”, “batshit crazy”, “batshit insane”, “shit nuts”, etc, to describe someone as completely off their rocker.
Where do they come from? The closest thing I could think of to a factual answer would be getting rabies from actual bat feces, leading to strange behavior or insanity.
I don’t know. If I had to guess I would suppose that is somehow related to the old ‘Batman’ TV series. Dick Grays, Bruce Wayne’s lover (I mean ‘ward’) was always saying ‘Holy Bat (something), Batman!’
I suppose that is it.
Uhhh, the bat butt?
I think it’s just an amusing construction. Apeshit is used the same way. Doubt it could be traced to a specific origin. Robin said “holy this” and “holy that” but not “holy bat this-or-that.” All of Batman’s stuff was that Batmobile, Bat Cave, Bat Plane, same Bat Time, same Bat Channel. But I think the phrase predates the popularity of Batman as brought by the TV show.
Everything on the show was Bat-This and Bat-That. Robin kept saying Holy This and Holy That. It is no wonder that as the show has been off the air for almost forty years that the to meld together.
“Apeshit” might have come from “going ape,” because people regularly vulgarize anything.
In the same way, you might get “batshit” from “going batty,” which does, actually, mean “insane.”
Bullshit.