tartar

Etymology 1

From Old French tartre, from Medieval Latin tartarum, from Byzantine Greek τάρταρον (tártaron), said to be from Arabic دُرْدِيّ (durdiyy), though it is already found in Pelagonius’s Ars veterinaria 46 in the adjective tartarālis, if the reading is correct.

noun

1. A red compound deposited during wine making; mostly potassium hydrogen tartrate — a source of cream of tartar.
2. A hard yellow deposit on the teeth, formed from dental plaque.

Etymology 2

From figurative use of Tartar.

noun

1. (dated) A fearsome or angrily violent person.
   Mrs. Begg said she liked Mrs. Dain, who was a sensible woman and a first-rate housewife, but that Gabrielle was a tartar. 1929, Dashiell Hammett, chapter 3, in The Dain Curse, New York: Vintage, published 1972, page 28