Nostalgia is a sentimentality for the past, typically for a period or place with happy personal associations. The word nostalgia is a neoclassical compound derived from Greek, consisting of νόστος (nóstos), a Homeric word meaning "homecoming", and ἄλγος (álgos), meaning "pain"; the word was coined by a 17th-century medical student to describe the anxieties displayed by Swiss mercenaries fighting away from home. Described as a medical condition—a form of melancholy—in the early modern period, it became an important trope in Romanticism.
https://en.wikipedia.org/wiki/Nostalgia