jar (v.) Look up jar at Dictionary.com
1520s, "to make a brief, harsh, grating sound," often in reference to bird screeches; the word often is said to be echoic or imitative; compare jargon (n.), jay (n.), garrulous. Figurative sense of "have an unpleasant effect on" is from 1530s; that of "cause to vibrate or shake" is from 1560s. Related: Jarred; jarring. As a noun in this sense from 1540s.
jar (n.) Look up jar at Dictionary.com
"simple earthen or glass cylindrical vessel," early 15c., possibly from Old French jarre "liquid measure smaller than a barrel" (12c.), perhaps from Provençal jarra, from Arabic jarrah "earthen water vessel, ewer" (whence also Spanish jarra, Italian giarra), which is from Persian jarrah "a jar, earthen water-vessel."