sympathetic

Where it comes from

Sympathetic ordinarily means showing understanding or compassion; also responding in harmony with something else. Sympathetic came through Modern Latin from Late Greek sympathetikos. Its family is based on Greek sympatheia, fellow feeling, and sympathes, affected by like feelings, from syn-, together, and pathos, experience, feeling, or suffering. English sympathy first covered affinities and shared influence, not only compassion.

How the meaning developed

That older breadth survives when strings vibrate sympathetically or body parts participate in a shared nervous response; concern for another became the dominant everyday sense later.