The Collaborative International Dictionary of English v.0.48:

Setterwort \Set"ter*wort`\, n. (Bot.)
   The bear's-foot (Helleborus f[oe]tidus); -- so called
   because the root was used in settering, or inserting setons
   into the dewlaps of cattle. Called also pegroots. --Dr.
   Prior.
   [1913 Webster]

WordNet (r) 3.0 (2006):

setterwort
    n 1: digitate-leaved hellebore with an offensive odor and
         irritant qualities when taken internally [syn: stinking
         hellebore, bear's foot, setterwort, Helleborus
         foetidus]