Nostalgia

The term nostalgia describes a sentimental longing for the past, typically for a period or place with happy personal associations. The word is a learned formation of a Greek compound, consisting of νόστος (nóstos), meaning "homecoming", a Homeric word, and ἄλγος (álgos), meaning "pain, ache". It was described as a medical condition, a form of melancholy, in the Early Modern period, and became an important trope in Romanticism.

In common, less clinical usage, nostalgia sometimes includes a general interest in past eras and their personalities and events, especially the "good old days," such as a sudden image, or remembrance of something from one's childhood.

The scientific literature on nostalgia is quite thin, but there are a few studies that have attempted to pin down the essence of nostalgia, and what causes it. Smell and touch are also strong evokers of nostalgia and memories in general due to the processing of these stimuli first passing through the amygdala, the emotional seat of the brain. These recollections of our past are usually important events, people we care about, and places where we have spent time. Music can also be a strong trigger of nostalgia.

A 17th Century medical student coined the term "nostalgia" for anxieties displayed by Swiss mercenaries fighting away from home, although some military doctors believed their problems were specific to the Swiss and caused by the Alpine racket of cowbells.