> It comes from the 1940's originally

Really?! That’s amazingly early. There were barely even subroutine libraries at that time. I’d love to see an example of "Application Programming Interface" from that time.

(I don’t remember seeing the term until Microsoft started using it when talking about Windows in the 1990s; before then it was things like library functions or supervisor calls - but I didn’t have much experience at that point so I was probably missing some of the more collar-and-tie programmer lingo.)