tart
adj.
"having a sharp taste," 1520s, also attested once, obscurely, from late 14c., perhaps from Old English teart "painful, sharp, severe, rough" (in reference to punishment, pain, suffering), from Germanic *ter-t-, from PIE *der- (2) "to split, flay, peel" (see tear, v.1), but the gap in the record is unexplained. Figurative use, with reference to words, speech, etc., is attested from c.1600. Related: Tartly; tartness, both also absent in Middle English.
n.
1
"small pie," late 14c., from Old French tarte "flat, open-topped pastry" (13c.), possibly an alteration of torte, from Late Latin torta "round loaf of bread" (in Medieval Latin "a cake, tart"), perhaps from past participle of torquere "to twist."
2
1887, "prostitute, immoral woman," from earlier use as a term of endearment to a girl or woman (1864), sometimes said to be a shortening of sweetheart. But another theory traces it to jam-tart (see tart, n.1), which was British slang early 19c. for "attractive woman." Diminutive tartlet attested from 1890. To tart (something) up is from 1938. Related: Tarted.