Are yams and sweet potatoes the same?
mid-14c. (as a surname late 13c.), from Old French pestel, from Latin pistillum "pounder, pestle," related to pinsere "to pound," from PIE *pis-to-, suffixed form of root *peis- "to crush" (cf. Sanskrit pinasti "pounds, crushes," pistah "anything ground, meal," Greek ptissein "to winnow," Old Church Slavonic pišo, pichati "to push, thrust, strike," pišenica "wheat," Russian pseno "millet").
pestle pes·tle (pěs'əl, pěs'təl)
A club-shaped, hand-held tool for grinding or mashing substances in a mortar.
ancient device for milling by pounding. Together with the saddle quern (a round stone rolled or rubbed on a flat stone bed), it was the first means known for grinding grain; the grain was placed in a shallow depression in a stone, the mortar, and pounded with a rodlike stone, the pestle. Refined versions of the mortar and pestle have continued to find use in kitchens for preparing pastes and other finely ground elements of cuisine, in pharmacy for preparing medicines, and in chemical laboratories.