"having a sharp taste," late 14c., perhaps from O.E. teart "painful, sharp, severe" (in ref. to punishment, pain, suffering), of unknown origin; possibly related to the root of teran "to tear." Fig. use, with ref. to words, speech, etc., is attested from c.1600.
"small pie," c.1400, from O.Fr. tarte "flat, open-topped pastry" (13c.), possibly an alteration of torte, from L.L. torta "round loaf of bread" (in M.L. "a cake, tart"), infl. in M.E. by tart (adj.).
"prostitute," 1887, 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." To tart (something) up is from 1938.