As I've written before, "Nostalgie de la boue" is a French phrase for "nostalgia for the mud". This site explains the meaning of the phrase:

"Nostalgie de la boue" means ascribing higher spiritual values to people and cultures considered "lower" than oneself, the romanticization of the faraway primitive which is also the equivalent of the lower class close to home. I have been submerged in such ideas since I was born and am just getting my head out of the waters. My parents romanticized Hungarian folk culture — my father photographed and published peasant architecture, my mother wore folk dresses, my uncle and father promoted native handicrafts in the weaving workshops they organized in the 1930's. I went much further in romanticizing the seemingly most unromantic Aztecs, leaping across an ocean, a continent and five centuries in revalidation.