being as how a "top" is the guy DOING the poking and a bottom is the guy receiving (ie: pitching and catching)
I would have to say that topping from the bottom would be the guy on the bottom who normally receives is doing the guy on top....(while he is on top)
Sheesh, just when you thought you knew everything, out comes another term...
Sheesh, it is like gays have a different word for everything!