nostalgia: [18] Etymologically, nostalgia is pain connected with returning home – in other words, homesickness. It is a modern coinage, based ultimately on Greek nostos ‘homecoming’ and algos ‘pain, grief’ (as in analgesic [19] and neuralgia (see NEURAL)). At first it was used as the name of what was regarded virtually as a form of mental illness (the earliest known record of it is in the journal kept by the botanist and explorer Joseph Banks on Captain Cook’s round-the-world voyage, in which he noted (1770) that most of the ship’s company were ‘now pretty far gone with the longing for home which the Physicians have gone so far as to esteem a disease under the name of Nostalgia’).
The milder present-day connotations of wistful longing for a past time emerged in the early 20th century. [nostalgia etymology, nostalgia origin, 英语词源]