"bitartrate of potash" (a deposit left during fermentation), late 14c., from Old French tartre, from Medieval Latin tartarum, from late Greek tartaron "tartar encrusting the sides of wine casks," perhaps of Semitic origin, but if so the exact source has not been identified; Arabic is unlikely because of the early date of the word in Latin. The purified substance is cream of tartar. Used generally in 17c. of encrustations from liquid contact; specific meaning "encrustation on teeth" (calcium phosphate) is first recorded 1806.
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Definitions of Tatar from WordNet
a member of the Mongolian people of central Asia who invaded Russia in the 13th century;