goût du terroir = earthy taste - also (with wine grapes) the terroir gives its qualities to the wine - calcaire for Champagne, rocky metal for Chablis, alluvial estuary soil for Bordeaux and so on.
I don't like the word "elusive" which just means it's difficult to define or find this earthy taste ???? introuvable ? or caché ?
Un goût caché du terroir??? - don't like that much, sorry!