Well I am a Dyson repairer in Australia but I am not sure that my answer will satisfy you.
I have always thought the idea of a "root" cyclone was a really odd name, there is nothing else here that I can think of that uses this word.
However I think the reason for that for this is that we call having sex a "root".
Well not the upper class but regular bogans for sure will say i can't wait to finish work so I can get a root!.
Unfortunately why it is called radix I have no idea other than it is not a well known word so it just sounds technical.
This is just supposition mind you I am far from a scholar just an educated guess.