I don't get the connection between the terms "apeshit" and crazy

Apeshit is usually connected with anger, when primates are annoyed, they throw poo at whoever is bothering them. It is usually "batshit" that is associated with crazy.

I know right!?
Everyone knows it's batshit crazy.

You don't think throwing feces is a certain level of cray?

Something be so crazy that the ape shit himself?

Cause they pick it up and throw it around