Sehnsucht (German) is the longing or yearning for something unachievable by someone, be it love or some of the motives common in the romanticism like travel and freedom.
1: Oh, sweet life why can't i be free and head out to and see the world.
Person A: Hey... I just got this old-fashioned TV the other day... Even if I never had one, I still feel nostalgia for it.
Person B: That's called Sehnsucht.