jar (v.) Look up jar at Dictionary.com
1520s, "to make a harsh, grating sound," usually said to be echoic or imitative, but no one explains how, or of what. Figurative sense of "have an unpleasant effect on" is from 1530s; that of "cause to vibrate or shake" is from 1560s. Related: Jarred; jarring.
jar (n.) Look up jar at Dictionary.com
"cylindrical vessel," early 15c., possibly from Middle French jarre "liquid measure" (smaller than a barrel), 12c., from Provençal jarra, from Arabic jarrah "earthen water vessel" (whence also Spanish jarra, Italian giarra) [Klein].