Slip Roll

[Gorton mill]

Thought I could find the answer to my 2 questions somewhere on the internet but have not been successful.
First, I'm wanting to know what the name is for each of the 3 rolls on a slip roll former. There's the driven roll - usually the bottom most roll. There's the top roll that is usually gear driven by the bottom roll and is adjusted to the metal's thickness and then there's the movable roll that sits off to the side and is adjusted to form the metal into a curve or ring. Anyone got the answers?
2nd question - why is the machine called a "slip roll"?

 

[C-Bag]

It’s called a slip roll because the the top roll has a release mechanism on one side that allows you get a roll you’ve formed off the machine. To “slip” it off one side.

 

[keeena]

In my Pexto's slip roll manual, they are just simply called lower (the directly driven one), upper (gear-driven), and rear rolls. There are some slip rolls which have a driven rear roll too; was an option with my Pexto.