The German word for homesickness is “heimweh.” Legend has it that Swiss mercenaries from the fifteenth century onward, dispersed throughout Europe to fight foreign wars, were hardy soldiers susceptible to few weaknesses. But they missed home with a deranging intensity, longing for the high elevation of their cantons, their clear lakes, their protective peaks. This feeling they called, in their Swiss German, heimweh. The intense psychosomatic disorder was first treated in 1688 by a physician in Switzerland, Johannes Hofer, who also gave it the Greek name “nostalgia.” It entered the English language in the late eighteenth century as “homesickness.”
Heimweh, having been absorbed into standard German, acquired an antonym, fernweh. Fernweh is a longing to be away from home, a desire to be in faraway places. Fernweh is similar to wanderlust but, like heimweh, has a sickish, melancholy tinge.

— Teju Cole, Known and Strange Things, Faber & Faber, Ch. Far Away From Here, 2016