> As far as I can tell, the idea of (explicit) reference counting came from Next,

Maybe in objc, but in the general case I kinda doubt this. It's a very common pattern in kernel development as an example, haven't done any archeology here but I have seen it in codebases rooted in the 80s at latest, probably earlier. (Did original Unix reference count file objects in the FD table the same way a modern kernel would? Would not be surprised if yes.)

Autorelease is pretty unique though and clever.