Well, I would have thought poll as in head, but Paul Burke has thrown up this curious reference to a "seesaw" meaning, so perhaps we are looking at a "pole for going up and down on"? I want to see chapter and verse for an early "seesaw" usage. I am not entireely clear why rantipole also means the wild carrot(Queen Ann's Lace) plant. Plants are not normally famous for jumping up and down, or behaving badly, or preaching loudly at people. All very curious.