[PAClearner]

we call them hidden layers because of path dependence i.e. that is what people called them at first.

the first neural network-like things would have input nodes directly connected to output nodes. Thus both layers were 'exposed' and visible. The hiddden layers are 'hidden' because you don't directly touch them or use them-they are obscured. You can call them intermediate layers if you want I suppose-people will probably understand what you mean