Some words from a spinner, here. The first Sunday after Twelfth Night us spinners get together to celebrate Rock Day, which is the day the spinners traditionally go back to work after the Christmas holiday.
It sounds like the rock being the distaff is correct from the scholarly information above. I've always been told the rock referred to the wheel itself. In German, I am told, the wheel is referred to as rocken. I've always been told that is the origion. Don't know, only gotten it by word of mouth.
A reel is also sometimes called a swift. I've got a nifty plastic one from Japan, but I've seen ones made out of whale bone. Modern ones of quality are made of wood. Pop goes the weasle also refers to this, as noted above. A weasle is also called a click reel, as it pops or clicks when so many yards have been wound on.
A distaff is what you use to hold your fiber so you can spin is. Distaffs in my experience are mostly used to hold flax, a plant fiber which when spun is called linen. A distaff is neccessary when spinning very long fibers, but not as neccessary when spinning wool, which can easily be held in the hand.
Whew!