bis·tort 
(bĭstôrt′)
(bĭstôrt′)n.
Any of several plants of the family Polygonaceae, especially the Eurasian perennial herb Persicaria bistorta (syn. Polygonum bistorta), having spikes of usually pink flowers and twisted roots used as an astringent in folk medicine.
[French bistorte, from Old French, from Medieval Latin *bistorta : Latin bis, twice; see BIS + torta, past participle of torquēre, to twist; see TORQUE1.]