Unpleasantly shocking or sudden; creating a harsh, discordant effect on the senses or emotions.
From 'jar' (to shake or vibrate), which comes from Middle English and onomatopoeia—it imitates the sound of a harsh collision. The '-ing' creates the adjective form.
Jarring is onomatopoeia at heart—it literally imitates the sound a jar makes when it collides! Your ears and your feelings both experience 'jar' the same way, showing how sound-sense links to emotion-sense.
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