Desiderium ...

 

... comes from the word desiderare, meaning to long for. Connections between desiderium and nostalgia have also been drawn; the former can be seen as expressing the latter for things that can't be experienced any more, or things that someone may have never experienced themselves. Paul Simon's The Only Living Boy in New York City always makes me feel that way. I was as old when I first heard it at twenty as I am today. Maybe older.