In music, Stigma is Vinnie Stigma from Agnostic Front solo band. In psychology, stigma is negative attitudes attached to a mental disorder.
The stigma is the part of the flower where the pollen grains stick during pollination
it is the sticky part on the end of the style that collects pollen
The stigma is sticky so that it can pick up the pollen grains easier, or, in other words, so that the pollen wll stick to it.
So the pollen will stick.